Ph sensing for sensor enabled negative pressure wound monitoring and therapy apparatuses

ABSTRACT

Embodiments of apparatuses, systems, methods for monitoring wound pH are disclosed. In some embodiments, a wound dressing includes one or more optical sensors configured to measure a change in color of a pH-sensitive adhesive that changes color in response to changes in wound exudate pH. In some embodiments, the wound dressing may further comprise hydrophilic channels that direct wound exudate to a pH-sensitive material over the optical sensors. Such dressings may also be used in combination with a negative pressure wound therapy system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/564,126, filed Sep. 27, 2017 and entitled, PH SENSING FOR SENSORENABLED NEGATIVE PRESSURE WOUND MONITORING AND THERAPY APPARATUSES; thedisclosure of which is hereby incorporated by reference in its entirety.

FIELD

Embodiments described herein relate to apparatuses, systems, and methodsfor the monitoring or treatment of wounds, for example using dressingsthat sense pH of a wound.

BACKGROUND

The treatment of open or chronic wounds that are too large tospontaneously close or otherwise fail to heal by means of applyingnegative pressure to the site of the wound is well known in the art.Negative pressure wound therapy (NPWT) systems currently known in theart commonly involve placing a cover that is impermeable orsemi-permeable to fluids over the wound, using various means to seal thecover to the tissue of the patient surrounding the wound, and connectinga source of negative pressure (such as a vacuum pump) to the cover in amanner so that negative pressure is created and maintained under thecover. It is believed that such negative pressures promote wound healingby facilitating the formation of granulation tissue at the wound andassisting the body's normal inflammatory process while simultaneouslyremoving excess fluid, which may contain adverse cytokines and/orbacteria. However, further improvements in NPWT are needed to fullyrealize the benefits of treatment.

Many different types of wound dressings are known for aiding in NPWTsystems. These different types of wound dressings include many differenttypes of materials and layers, for example, gauze, pads, foam pads ormulti-layer wound dressings. Topical negative pressure therapy,sometimes referred to as vacuum assisted closure, negative pressurewound therapy, or reduced pressure wound therapy, is widely recognizedas a beneficial mechanism for improving the healing rate of a wound.Such therapy is applicable to a broad range of wounds such as incisionalwounds, open wounds and abdominal wounds or the like.

One example of a multi-layer wound dressing is the PICO dressing,available from Smith & Nephew, which includes a wound contact layer anda superabsorbent layer beneath a backing layer to provide acanister-less system for treating a wound with NPWT. The wound dressingmay be sealed to a suction port providing connection to a length oftubing, which may be used to pump fluid out of the dressing and/or totransmit negative pressure from a pump to the wound dressing.Additionally, RENASYS-F, RENASYS-G, RENASYS-AB, and RENASYS-F/AB,available from Smith & Nephew, are additional examples of NPWT wounddressings and systems. Another example of a multi-layer wound dressingis the ALLEVYN Life dressing, available from Smith & Nephew, whichincludes a moist wound environment dressing that is used to treat thewound without the use of negative pressure.

The pH of a wound bed may provide valuable information regarding thestate of wound healing. For example, researchers have found thatprolonged chemical acidification of a wound bed may increase the healingrate in chronic wounds, speculating that such improved healing involvesan increase in tissue oxygen availability through oxygen dissociationand reduced toxicity of bacterial end products, therefore stimulatingwound healing. Chronic wound fluids generally contain elevated proteaselevels, which may have deleterious effects on wound healing, degradingde novo granulation tissue and endogenous, biologically active proteinssuch as growth factors and cytokines. The wound bed pH of chronic woundstends to be alkaline or neutral (approximately pH of 7-8) when comparedto intact surrounding skin (approximately pH of 5.5) but the pH of achronic wound trends toward an acidic state during epithelialization.Protease activity is pH sensitive, peaking at about pH 7-8, butdecreasing rapidly under more acidic conditions. When a wound is keptunder more acidic condition, the fibroblasts proliferate more activelyand the wound's healing process is stimulated to a greater extent thanwhen in a neutral or alkaline condition.

However, prior art dressings for use in negative pressure wound therapyor other wound therapy provide little visualization or information ofthe condition of the wound beneath the dressing. This can require thedressing to be changed prematurely before the desired level of woundhealing has occurred or, for absorbent dressings, prior to the fullabsorbent capacity of the dressing being reached to allow the clinicianto inspect the healing and status of the wound. Some current dressingshave limited and/or unsatisfactory methods or features of providinginformation of conditions of the wound, such as the pH. Therefore,improved monitoring of wound healing and/or wound pH is desirable.

Additionally, nearly all areas of medicine may benefit from improvedinformation regarding the state of the tissue, organ, or system to betreated, particularly if such information is gathered in real-timeduring treatment. Many types of treatments are still routinely performedwithout the use of sensor data collection; instead, such treatments relyupon visual inspection by a caregiver or other limited means rather thanquantitative sensor data. For example, in the case of wound treatmentvia dressings and/or negative pressure wound therapy, data collection isgenerally limited to visual inspection by a caregiver and often theunderlying wounded tissue may be obscured by bandages or other visualimpediments. Even intact, unwounded skin may have underlying damage thatis not visible to the naked eye, such as a compromised vascular ordeeper tissue damage that may lead to an ulcer. Similar to woundtreatment, during orthopedic treatments requiring the immobilization ofa limb with a cast or other encasement, only limited information isgathered on the underlying tissue. In instances of internal tissuerepair, such as a bone plate, continued direct sensor-driven datacollection is not performed. Further, braces and/or sleeves used tosupport musculoskeletal function do not monitor the functions of theunderlying muscles or the movement of the limbs. Outside of directtreatments, common hospital room items such as beds and blankets couldbe improved by adding capability to monitor patient parameters.

Therefore, there is a need for improved sensor monitoring, particularlythrough the use of sensor-enabled substrates which can be incorporatedinto existing treatment regimes.

SUMMARY

Some embodiments of the present disclosure relate to wound dressings.Some embodiments relate to wound monitoring systems. Some embodimentsrelate to methods of using wound dressings or wound monitoring systems.

In some embodiments, a wound monitoring system includes a wound dressingand a controller. The wound dressing is configured to be positioned incontact with a wound and the wound dressing includes a plurality ofsensors. The plurality of sensors is configured to measure a pluralityof wound characteristics. The controller includes one or moreprocessors. The controller is configured to be communicatively coupledto at least some of the plurality of sensors. In some embodiments, a kitmay include any of the wound dressings described herein and/or any othercomponent or feature described herein, for example a negative pressuresource configured to be fluidically connected to the wound dressing.

In particular embodiments, a wound monitoring system comprises a wounddressing configured to be positioned in contact with a wound, the wounddressing comprising an optical sensor configured to measure a color; anda pH-sensitive material positioned on an underside of the wounddressing, the pH-sensitive material configured to change color inresponse to a change in a pH of the wound, wherein the optical sensor isfurther configured to detect the pH of the wound based on detection inthe color change of the pH-sensitive material.

In some embodiments, the system may further comprise a non-pH-sensitivematerial positioned on the underside of the wound dressing, thenon-pH-sensitive material configured to direct wound exudate to thepH-sensitive material. pH-sensitive material may comprise a gel or afoam. The non-pH-sensitive material may also comprise a gel or a foamand the gel or foam may be hydrophilic. The pH-sensitive material may beinterspersed with pH-sensitive elements prior to formation of the gel orfoam. The pH-sensitive elements may be dispersed heterogeneously. Inembodiments, the pH-sensitive elements may be dispersed homogeneously.The non-pH-sensitive material may be configured to direct wound exudateto the pH-sensitive material. The non-pH material may be arranged as oneor more channels on the underside of the wound dressing. The one or morechannels may extend from the pH-sensitive material to an edge of thedressing. In certain embodiments, the system further comprises acontroller, the controller configured to convert the color measured bythe optical sensor to a pH value. The controller is configured toprovide an indication of the pH value to a user. The controller may befurther configured to display the pH value. In some embodiments, thepH-sensitive material may comprise adhesive material. In embodiments,the non-pH-sensitive material may comprise adhesive material. ThepH-sensitive material may comprise a polyurethane.

In certain embodiments, a system such as described above may include areference material, the reference material configured to maintain astable color. The reference material may be incorporated into the wounddressing or be separate from the dressing.

In some embodiments, a method of monitoring the pH of a wound maycomprise:

monitoring at least one of a wound or skin surrounding a wound with awound dressing positioned in contact with the wound or skin surroundingthe wound, the wound dressing comprising a pH-sensitive materialconfigured to change color in response to a change in a pH of the woundand an optical sensor configured to detect a color change of thepH-sensitive material; and

computing with a processor a pH value based on the detected color changefrom the optical sensor.

In certain embodiments, the optical sensor may be configured to detect acolor value of a reference material, and further normalizing a colorvalue of the pH-sensitive material to the reference material. Thereference material may be configured to maintain a stable color.

Any of the features, components, or details of any of the arrangementsor embodiments disclosed in this application, including withoutlimitation any of the pump embodiments and any of the negative pressurewound therapy embodiments disclosed below, are interchangeablycombinable with any other features, components, or details of any of thearrangements or embodiments disclosed herein to form new arrangementsand embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a negative pressure wound treatment system employinga flexible fluidic connector and a wound dressing capable of absorbingand storing wound exudate according to some embodiments;

FIG. 1B illustrates a negative pressure wound treatment system employinga flexible fluidic connector and a wound dressing capable of absorbingand storing wound exudate according to some embodiments;

FIG. 2A illustrates a negative pressure wound treatment system employinga flexible fluidic connector and a wound dressing capable of absorbingand storing wound exudate according to some embodiments;

FIG. 2B illustrates a cross section of a fluidic connector connected toa wound dressing according to some embodiments;

FIG. 2C illustrates of a negative pressure wound therapy systemaccording to some embodiments;

FIG. 2D illustrates a wound treatment system employing a wound dressingcapable of absorbing and storing wound exudate to be used withoutnegative pressure according to some embodiments;

FIG. 3A illustrates a sensor array illustrating the sensor placementincorporated into a wound dressing component according to someembodiments;

FIG. 3B illustrates a flexible sensor array including a sensor arrayportion, a tail portion, and a connector pad end portion according tosome embodiments;

FIGS. 3C-3F show embodiments of the flexible circuit boards with fourdifferent sensor array geometries;

FIG. 3G shows an embodiment of the sensor array portion of the sensorarray design shown in FIG. 3D in more detail;

FIG. 3H illustrates a flexible sensor array incorporated into aperforated wound contact layer according to some embodiments;

FIG. 3I illustrates a block diagram of a control module according tosome embodiments;

FIG. 4 illustrates an embodiment of a method for monitoring the pH in awound;

FIG. 5 depicts an embodiment of a wound therapy system employing adressing including a pH-sensitive material beneath a plurality ofsensors configured to detect changes in pH;

FIG. 6 depicts a bottom side of an embodiment of a wound therapy systememploying a wound dressing including channels for directing woundexudate to a sensor configured to detect changes in pH;

FIG. 7 depicts an embodiment of a method for normalizing a sensorconfigured to detect changes in pH.

DETAILED DESCRIPTION

Embodiments disclosed herein relate to apparatuses and methods ofmonitoring and treating biological tissue with sensor-enabledsubstrates. The embodiments disclosed herein are not limited totreatment or monitoring of a particular type of tissue or injury,instead the sensor-enabled technologies disclosed herein are broadlyapplicable to any type of therapy that may benefit from sensor-enabledsubstrates. Some implementations utilize sensors and data collectionrelied upon by health care providers to make both diagnostic and patientmanagement decisions. International Patent Application No.PCT/IB2017/000693, filed May 5, 2017 titled “SENSOR ENABLED NEGATIVEPRESSURE WOUND THERAPY APPARATUS,” published as WO 2017/195038, theentirety of which is hereby incorporated by reference, describes variousexample embodiments and features related to sensors, apparatuses,systems, and methods the treatment of wounds, for example usingdressings in combination with negative pressure wound therapy.

Some embodiments disclosed herein relate to the use of sensors mountedon or embedded within substrates configured to be used in the treatmentof both intact and damaged human or animal tissue. Such sensors maycollect information about the surrounding tissue and transmit suchinformation to a computing device or a caregiver to be utilized infurther treatment. In certain embodiments, such sensors may be attachedto the skin anywhere on the body, including areas for monitoringarthritis, temperature, or other areas that may be prone to problems andrequire monitoring. Sensors disclosed herein may also incorporatemarkers, such as radiopaque markers, to indicate the presence of thedevice, for example prior to performing an MRI or other technique.

The sensor embodiments disclosed herein may be used in combination withclothing. Non-limiting examples of clothing for use with embodiments ofthe sensors disclosed herein include shirts, pants, trousers, dresses,undergarments, outer-garments, gloves, shoes, hats, and other suitablegarments. In certain embodiments, the sensor embodiments disclosedherein may be welded into or laminated into/onto the particulargarments. The sensor embodiments may be printed directly onto thegarment and/or embedded into the fabric. Breathable and printablematerials such as microporous membranes may also be suitable.

Sensor embodiments disclosed herein may be incorporated into cushioningor bed padding, such as within a hospital bed, to monitor patientcharacteristics, such as any characteristic disclosed herein. In certainembodiments, a disposable film containing such sensors could be placedover the hospital bedding and removed/replaced as needed.

In some implementations, the sensor embodiments disclosed herein mayincorporate energy harvesting, such that the sensor embodiments areself-sustaining. For example, energy may be harvested from thermalenergy sources, kinetic energy sources, chemical gradients, or anysuitable energy source.

The sensor embodiments disclosed herein may be utilized inrehabilitation devices and treatments, including sports medicine. Forexample, the sensor embodiments disclosed herein may be used in braces,sleeves, wraps, supports, and other suitable items. Similarly, thesensor embodiments disclosed herein may be incorporated into sportingequipment, such as helmets, sleeves, and/or pads. For example, suchsensor embodiments may be incorporated into a protective helmet tomonitor characteristics such as acceleration, which may be useful inconcussion diagnosis.

The sensor embodiments disclosed herein may be used in coordination withsurgical devices, for example, the NAVIO surgical system by Smith &Nephew Inc. In implementations, the sensor embodiments disclosed hereinmay be in communication with such surgical devices to guide placement ofthe surgical devices. In some implementations, the sensor embodimentsdisclosed herein may monitor blood flow to or away from the potentialsurgical site or ensure that there is no blood flow to a surgical site.Further surgical data may be collected to aid in the prevention ofscarring and monitor areas away from the impacted area.

To further aid in surgical techniques, the sensors disclosed herein maybe incorporated into a surgical drape to provide information regardingtissue under the drape that may not be immediately visible to the nakedeye. For example, a sensor embedded flexible drape may have sensorspositioned advantageously to provide improved area-focused datacollection. In certain implementations, the sensor embodiments disclosedherein may be incorporated into the border or interior of a drape tocreate fencing to limit/control the surgical theater.

Sensor embodiments as disclosed herein may also be utilized forpre-surgical assessment. For example, such sensor embodiments may beused to collect information about a potential surgical site, such as bymonitoring skin and the underlying tissues for a possible incision site.For example, perfusion levels or other suitable characteristics may bemonitored at the surface of the skin and deeper in the tissue to assesswhether an individual patient may be at risk for surgical complications.Sensor embodiments such as those disclosed herein may be used toevaluate the presence of microbial infection and provide an indicationfor the use of antimicrobials. Further, sensor embodiments disclosedherein may collect further information in deeper tissue, such asidentifying pressure ulcer damage and/or the fatty tissue levels.

The sensor embodiments disclosed herein may be utilized incardiovascular monitoring. For example, such sensor embodiments may beincorporated into a flexible cardiovascular monitor that may be placedagainst the skin to monitor characteristics of the cardiovascular systemand communicate such information to another device and/or a caregiver.For example, such a device may monitor pulse rate, oxygenation of theblood, and/or electrical activity of the heart. Similarly, the sensorembodiments disclosed herein may be utilized for neurophysiologicalapplications, such as monitoring electrical activity of neurons.

The sensor embodiments disclosed herein may be incorporated intoimplantable devices, such as implantable orthopedic implants, includingflexible implants. Such sensor embodiments may be configured to collectinformation regarding the implant site and transmit this information toan external source. In some embodiments, an internal source may alsoprovide power for such an implant.

The sensor embodiments disclosed herein may also be utilized formonitoring biochemical activity on the surface of the skin or below thesurface of the skin, such as lactose buildup in muscle or sweatproduction on the surface of the skin. In some embodiments, othercharacteristics may be monitored, such as glucose concentration, urineconcentration, tissue pressure, skin temperature, skin surfaceconductivity, skin surface resistivity, skin hydration, skin maceration,and/or skin ripping.

Sensor embodiments as disclosed herein may be incorporated into Ear,Nose, and Throat (ENT) applications. For example, such sensorembodiments may be utilized to monitor recovery from ENT-relatedsurgery, such as wound monitoring within the sinus passage.

As described in greater detail below, the sensor embodiments disclosedherein may encompass sensor printing technology with encapsulation, suchas encapsulation with a polymer film Such a film may be constructedusing any polymer described herein, such as polyurethane. Encapsulationof the sensor embodiments may provide waterproofing of the electronicsand protection from local tissue, local fluids, and other sources ofpotential damage.

In certain embodiments, the sensors disclosed herein may be incorporatedinto an organ protection layer such as disclosed below. Such asensor-embedded organ protection layer may both protect the organ ofinterest and confirm that the organ protection layer is in position andproviding protection. Further, a sensor-embedded organ protection layermay be utilized to monitor the underlying organ, such as by monitoringblood flow, oxygenation, and other suitable markers of organ health. Insome embodiments, a sensor-enabled organ protection layer may be used tomonitor a transplanted organ, such as by monitoring the fat and musclecontent of the organ. Further, sensor-enabled organ protection layersmay be used to monitor an organ during and after transplant, such asduring rehabilitation of the organ.

The sensor embodiments disclosed herein may be incorporated intotreatments for wounds (disclosed in greater detail below) or in avariety of other applications. Non-limiting examples of additionalapplications for the sensor embodiments disclosed herein include:monitoring and treatment of intact skin, cardiovascular applicationssuch as monitoring blood flow, orthopedic applications such asmonitoring limb movement and bone repair, neurophysiologicalapplications such as monitoring electrical impulses, and any othertissue, organ, system, or condition that may benefit from improvedsensor-enabled monitoring.

Wound Therapy

Some embodiments disclosed herein relate to wound therapy for a human oranimal body. Therefore, any reference to a wound herein can refer to awound on a human or animal body, and any reference to a body herein canrefer to a human or animal body. The disclosed technology embodimentsmay relate to preventing or minimizing damage to physiological tissue orliving tissue, or to the treatment of damaged tissue (for example, awound as described herein) wound with or without reduced pressure,including for example a source of negative pressure and wound dressingcomponents and apparatuses. The apparatuses and components comprisingthe wound overlay and packing materials or internal layers, if any, aresometimes collectively referred to herein as dressings. In someembodiments, the wound dressing can be provided to be utilized withoutreduced pressure.

Some embodiments disclosed herein relate to wound therapy for a human oranimal body. Therefore, any reference to a wound herein can refer to awound on a human or animal body, and any reference to a body herein canrefer to a human or animal body. The disclosed technology embodimentsmay relate to preventing or minimizing damage to physiological tissue orliving tissue, or to the treatment of damaged tissue (for example, awound as described herein).

As used herein the expression “wound” may include an injury to livingtissue may be caused by a cut, blow, or other impact, typically one inwhich the skin is cut or broken. A wound may be a chronic or acuteinjury. Acute wounds occur as a result of surgery or trauma. They movethrough the stages of healing within a predicted timeframe. Chronicwounds typically begin as acute wounds. The acute wound can become achronic wound when it does not follow the healing stages resulting in alengthened recovery. It is believed that the transition from acute tochronic wound can be due to a patient being immuno-compromised.

Chronic wounds may include for example: venous ulcers (such as thosethat occur in the legs), which account for the majority of chronicwounds and mostly affect the elderly, diabetic ulcers (for example, footor ankle ulcers), peripheral arterial disease, pressure ulcers, orepidermolysis bullosa (EB).

Examples of other wounds include, but are not limited to, abdominalwounds or other large or incisional wounds, either as a result ofsurgery, trauma, sterniotomies, fasciotomies, or other conditions,dehisced wounds, acute wounds, chronic wounds, subacute and dehiscedwounds, traumatic wounds, flaps and skin grafts, lacerations, abrasions,contusions, burns, diabetic ulcers, pressure ulcers, stoma, surgicalwounds, trauma and venous ulcers or the like.

Wounds may also include a deep tissue injury. Deep tissue injury is aterm proposed by the National Pressure Ulcer Advisory Panel (NPUAP) todescribe a unique form of pressure ulcers. These ulcers have beendescribed by clinicians for many years with terms such as purplepressure ulcers, ulcers that are likely to deteriorate and bruises onbony prominences.

Wound may also include tissue at risk of becoming a wound as discussedherein. For example, tissue at risk may include tissue over a bonyprotuberance (at risk of deep tissue injury/insult) or pre-surgicaltissue (for example, knee tissue) that may has the potential to be cut(for example, for joint replacement/surgical alteration/reconstruction).

Some embodiments relate to methods of treating a wound with thetechnology disclosed herein in conjunction with one or more of thefollowing: advanced footwear, turning a patient, offloading (such as,offloading diabetic foot ulcers), treatment of infection, systemix,antimicrobial, antibiotics, surgery, removal of tissue, affecting bloodflow, physiotherapy, exercise, bathing, nutrition, hydration, nervestimulation, ultrasound, electrostimulation, oxygen therapy, microwavetherapy, active agents ozone, antibiotics, antimicrobials, or the like.

Alternatively or additionally, a wound may be treated using topicalnegative pressure and/or traditional advanced wound care, which is notaided by the using of applied negative pressure (may also be referred toas non-negative pressure therapy).

Advanced wound care may include use of an absorbent dressing, anocclusive dressing, use of an antimicrobial and/or debriding agents in awound dressing or adjunct, a pad (for example, a cushioning orcompressive therapy, such as stockings or bandages), or the like.

In some embodiments, treatment of such wounds can be performed usingtraditional wound care, wherein a dressing can be applied to the woundto facilitate and promote healing of the wound. Some embodiments relateto methods of manufacturing a wound dressing comprising providing awound dressing as disclosed herein. The wound dressings that may beutilized in conjunction with the disclosed technology include any knowndressing in the art. The technology is applicable to negative pressuretherapy treatment as well as non-negative pressure therapy treatment. Insome embodiments, a wound dressing comprises one or more absorbentlayer(s). The absorbent layer may be a foam or a superabsorbent.

In some embodiments, wound dressings may comprise a dressing layerincluding a polysaccharide or modified polysaccharide, apolyvinylpyrrolidone, a polyvinyl alcohol, a polyvinyl ether, apolyurethane, a polyacrylate, a polyacrylamide, collagen, or gelatin ormixtures thereof. Dressing layers comprising the polymers listed areknown in the art as being useful for forming a wound dressing layer foreither negative pressure therapy or non-negative pressure therapy.

In some embodiments, the polymer matrix may be a polysaccharide ormodified polysaccharide. In some embodiments, the polymer matrix may bea cellulose. Cellulose material may include hydrophilically modifiedcellulose such as methyl cellulose, carboxymethyl cellulose (CMC),carboxymethyl cellulose (CEC), ethyl cellulose, propyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethylcellulose, carboxyethyl sulphonate cellulose, cellulose alkylsulphonate, or mixtures thereof.

In certain embodiments, cellulose material may be cellulose alkylsulphonate. The alkyl moiety of the alkyl sulphonate substituent groupmay have an alkyl group having 1 to 6 carbon atoms, such as methyl,ethyl, propyl, or butyl. The alkyl moiety may be branched or unbranched,and hence suitable propyl sulphonate substituents may be 1- or2-methyl-ethylsulphonate. Butyl sulphonate substituents may be2-ethyl-ethylsulphonate, 2,2-dimethyl-ethylsulphonate, or1,2-dimethyl-ethylsulphonate. The alkyl sulphonate substituent group maybe ethyl sulphonate. The cellulose alkyl sulphonate is described inWO10061225, US2016/114074, US2006/0142560, or U.S. Pat. No. 5,703,225,the disclosures of which are hereby incorporated by reference in theirentirety.

Cellulose alkyl sulfonates may have varying degrees of substitution, thechain length of the cellulose backbone structure, and the structure ofthe alkyl sulfonate substituent. Solubility and absorbency are largelydependent on the degree of substitution: as the degree of substitutionis increased, the cellulose alkyl sulfonate becomes increasinglysoluble. It follows that, as solubility increases, absorbency increases.

In some embodiments, a wound dressing also comprises a top or coverlayer. The thickness of the wound dressing disclosed herein may bebetween 1 to 20, or 2 to 10, or 3 to 7 mm. In some embodiments, thedisclosed technology may be used in conjunction with a non-negativepressure dressing. A non-negative pressure wound dressing suitable forproviding protection at a wound site may comprise: an absorbent layerfor absorbing wound exudate and an obscuring element for at leastpartially obscuring a view of wound exudate absorbed by the absorbentlayer in use.

The obscuring element may be partially translucent. The obscuringelement may be a masking layer. The non-negative pressure wound dressingmay further comprise a region in or adjacent the obscuring element forallowing viewing of the absorbent layer. For example, the obscuringelement layer may be provided over a central region of the absorbentlayer and not over a border region of the absorbent layer. In someembodiments, the obscuring element is of hydrophilic material or iscoated with a hydrophilic material.

The obscuring element may comprise a three-dimensional knitted spacerfabric. The spacer fabric is known in the art and may include a knittedspacer fabric layer. The obscuring element may further comprise anindicator for indicating the need to change the dressing. In someembodiments, the obscuring element is provided as a layer at leastpartially over the absorbent layer, further from a wound site than theabsorbent layer in use.

The non-negative pressure wound dressing may further comprise aplurality of openings in the obscuring element for allowing fluid tomove therethrough. The obscuring element may comprise, or may be coatedwith, a material having size-exclusion properties for selectivelypermitting or preventing passage of molecules of a predetermined size orweight.

The obscuring element may be configured to at least partially mask lightradiation having wavelength of 600 nm and less. The obscuring elementmay be configured to reduce light absorption by 50% or more. Theobscuring element may be configured to yield a CIE L* value of 50 ormore, and optionally 70 or more. In some embodiments, the obscuringelement may be configured to yield a CIE L* value of 70 or more. In someembodiments, the non-negative pressure wound dressing may furthercomprise at least one of a wound contact layer, a foam layer, an odorcontrol element, a pressure-resistant layer and a cover layer.

In some embodiments, the cover layer is present, and the cover layer isa translucent film Typically, the translucent film has a moisture vapourpermeability of 500 g/m2/24 hours or more. The translucent film may be abacterial bather. In some embodiments, the non-negative pressure wounddressing as disclosed herein comprises the wound contact layer and theabsorbent layer overlies the wound contact layer. The wound contactlayer carries an adhesive portion for forming a substantially fluidtight seal over the wound site. The non-negative pressure wound dressingas disclosed herein may comprise the obscuring element and the absorbentlayer being provided as a single layer.

In some embodiments, the non-negative pressure wound dressing disclosedherein comprises the foam layer, and the obscuring element is of amaterial comprising components that may be displaced or broken bymovement of the obscuring element.

In some embodiments, the non-negative pressure wound dressing comprisesan odor control element, and in another embodiment the dressing does notinclude an odor control element. When present, the odor control elementmay be dispersed within or adjacent the absorbent layer or the obscuringelement. Alternatively, when present the odor control element may beprovided as a layer sandwiched between the foam layer and the absorbentlayer.

In some embodiments, the disclosed technology for a non-negativepressure wound dressing comprises a method of manufacturing a wounddressing, comprising: providing an absorbent layer for absorbing woundexudate; and providing an obscuring element for at least partiallyobscuring a view of wound exudate absorbed by the absorbent layer inuse.

In some embodiments, the non-negative pressure wound dressing may besuitable for providing protection at a wound site, comprising: anabsorbent layer for absorbing wound exudate; and a shielding layerprovided over the absorbent layer, and further from a wound-facing sideof the wound dressing than the absorbent layer. The shielding layer maybe provided directly over the absorbent layer. In some embodiments, theshielding layer comprises a three-dimensional spacer fabric layer.

The shielding layer increases the area over which a pressure applied tothe dressing is transferred by 25% or more or the initial area ofapplication. For example the shielding layer increases the area overwhich a pressure applied to the dressing is transferred by 50% or more,and optionally by 100% or more, and optionally by 200% or more. Theshielding layer may comprise 2 or more sub-layers, wherein a firstsub-layer comprises through holes and a further sub-layer comprisesthrough holes and the through holes of the first sub-layer are offsetfrom the through holes of the further sub-layer.

The non-negative pressure wound dressing as disclosed herein may furthercomprise a permeable cover layer for allowing the transmission of gasand vapour therethrough, the cover layer provided over the shieldinglayer, wherein through holes of the cover layer are offset from throughholes of the shielding layer. The non-negative pressure wound dressingmay be suitable for treatment of pressure ulcers.

A more detailed description of the non-negative pressure dressingdisclosed hereinabove is provided in WO2013007973, the entirety of whichis hereby incorporated by reference. In some embodiments, thenon-negative pressure wound dressing may be a multi-layered wounddressing comprising: a fibrous absorbent layer for absorbing exudatefrom a wound site; and a support layer configured to reduce shrinkage ofat least a portion of the wound dressing.

In some embodiments, the multi-layered wound dressing disclosed herein,further comprises a liquid impermeable film layer, wherein the supportlayer is located between the absorbent layer and the film layer. Thesupport layer disclosed herein may comprise a net. The net may comprisea geometric structure having a plurality of substantially geometricapertures extending therethrough. The geometric structure may forexample comprise a plurality of bosses substantially evenly spaced andjoined by polymer strands to form the substantially geometric aperturesbetween the polymer strands.

The net may be formed from high density polyethylene. The apertures mayhave an area from 0.005 to 0.32 mm2. The support layer may have atensile strength from 0.05 to 0.06 Nm. The support layer may have athickness of from 50 to 150 μm.

In some embodiments, the support layer is located directly adjacent theabsorbent layer. Typically, the support layer is bonded to fibers in atop surface of the absorbent layer. The support layer may furthercomprise a bonding layer, wherein the support layer is heat laminated tothe fibers in the absorbent layer via the bonding layer. The bondinglayer may comprise a low melting point adhesive such as ethylene-vinylacetate adhesive.

In some embodiments, the multi-layered wound dressing disclosed hereinfurther comprises an adhesive layer attaching the film layer to thesupport layer. In some embodiments, the multi-layered wound dressingdisclosed herein further comprises a wound contact layer locatedadjacent the absorbent layer for positioning adjacent a wound. Themulti-layered wound dressing may further comprise a fluid transportlayer between the wound contact layer and the absorbent layer fortransporting exudate away from a wound into the absorbent layer.

A more detailed description of the multi-layered wound dressingdisclosed hereinabove is provided in GB patent application filed on 28Oct. 2016 with application number GB1618298.2, the entirety of which ishereby incorporated by reference. In some embodiments, the disclosedtechnology may be incorporated in a wound dressing comprising avertically lapped material comprising: a first layer of an absorbinglayer of material, and a second layer of material, wherein the firstlayer being constructed from at least one layer of non-woven textilefibers, the non-woven textile fibers being folded into a plurality offolds to form a pleated structure. In some embodiments, the wounddressing further comprises a second layer of material that istemporarily or permanently connected to the first layer of material.

Typically the vertically lapped material has been slitted. In someembodiments, the first layer has a pleated structure having a depthdetermined by the depth of pleats or by the slitting width. The firstlayer of material may be a moldable, lightweight, fiber-based material,blend of material or composition layer.

The first layer of material may comprise one or more of manufacturedfibers from synthetic, natural or inorganic polymers, natural fibers ofa cellulosic, proteinaceous or mineral source. The wound dressing maycomprise two or more layers of the absorbing layer of materialvertically lapped material stacked one on top of the other, wherein thetwo or more layers have the same or different densities or composition.The wound dressing may in some embodiments comprise only one layer ofthe absorbing layer of material vertically lapped material.

The absorbing layer of material is a blend of natural or synthetic,organic or inorganic fibers, and binder fibers, or bicomponent fiberstypically PET with a low melt temperature PET coating to soften atspecified temperatures and to act as a bonding agent in the overallblend. In some embodiments, the absorbing layer of material may be ablend of 5 to 95% thermoplastic polymer, and 5 to 95 wt % of a celluloseor derivative thereof. In some embodiments, the wound dressing disclosedherein has a second layer comprises a foam or a dressing fixative. Thefoam may be a polyurethane foam. The polyurethane foam may have an openor closed pore structure.

The dressing fixative may include bandages, tape, gauze, or backinglayer. In some embodiments, the wound dressing as disclosed hereincomprises the absorbing layer of material connected directly to a secondlayer by lamination or by an adhesive, and the second layer is connectedto a dressing fixative layer. The adhesive may be an acrylic adhesive,or a silicone adhesive.

In some embodiments, the wound dressing as disclosed herein furthercomprises layer of a superabsorbent fiber, or a viscose fiber or apolyester fiber. In some embodiments, the wound dressing as disclosedherein further comprises a backing layer. The backing layer may be atransparent or opaque film. Typically the backing layer comprises apolyurethane film (typically a transparent polyurethane film). A moredetailed description of the multi-layered wound dressing disclosedhereinabove is provided in GB patent applications filed on 12 Dec. 2016with application number GB1621057.7; and 22 Jun. 2017 with applicationnumber GB1709987.0, the entirety of each of which is hereby incorporatedby reference.

In some embodiments, the non-negative pressure wound dressing maycomprise an absorbent component for a wound dressing, the componentcomprising a wound contacting layer comprising gel forming fibers boundto a foam layer, wherein the foam layer is bound directly to the woundcontact layer by an adhesive, polymer based melt layer, by flamelamination or by ultrasound. The absorbent component may be in a sheetform. The wound contacting layer may comprise a layer of woven ornon-woven or knitted gel forming fibers.

The foam layer may be an open cell foam, or closed cell foam, typicallyan open cell foam. The foam layer is a hydrophilic foam. The wounddressing may comprise the component that forms an island in directcontact with the wound surrounded by periphery of adhesive that adheresthe dressing to the wound. The adhesive may be a silicone or acrylicadhesive, typically a silicone adhesive. The wound dressing may becovered by a film layer on the surface of the dressing furthest from thewound.

A more detailed description of the wound dressing of this typehereinabove is provided in EP2498829, the entirety of which is herebyincorporated by reference. In some embodiments, the non-negativepressure wound dressing may comprise a multi layered wound dressing foruse on wounds producing high levels of exudate, characterized in thatthe dressing comprising: a transmission layer having an MVTR of at least300 gm2/24 hours, an absorbent core comprising gel forming fiberscapable of absorbing and retaining exudate, a wound contacting layercomprising gel forming fibers which transmits exudate to the absorbentcore and a keying layer positioned on the absorbent core, the absorbentcore and wound contacting layer limiting the lateral spread of exudatein the dressing to the region of the wound.

The wound dressing may be capable of handling at least 6 g (or 8 g and15 g) of fluid per 10 cm2 of dressing in 24 hours. The wound dressingmay comprise gel forming fibers that are chemically modified cellulosicfibers in the form of a fabric. The fibers may include carboxymethylatedcellulose fibers, typically sodium carboxymethylcellulose fiber. Thewound dressing may comprise a wound contact layer with a lateral wickingrate from 5 mm per minute to 40 mm per minute. The wound contact layermay have a fiber density between 25 gm2 and 55 gm2, such as 35 gm2. Theabsorbent core may have an absorbency of exudate of at least 10 g/g, andtypically a rate of lateral wicking of less the 20 mm per minute. Theabsorbent core may have a blend in the range of up to 25% cellulosicfibers by weight and 75% to 100% gel forming fibers by weight.

Alternatively, the absorbent core may have a blend in the range of up to50% cellulosic fibers by weight and 50% to 100% gel forming fibers byweight. For example the blend is in the range of 50% cellulosic fibersby weight and 50% gel forming fibers by weight. The fiber density in theabsorbent core may be between 150 gm2 and 250 gm2, or about 200 gm2. Thewound dressing when wet may have shrinkage that is less than 25% or lessthan 15% of its original size/dimension. The wound dressing may comprisea transmission layer and the layer is a foam. The transmission layer maybe a polyurethane foam laminated to a polyurethane film.

The wound dressing may comprise one or more layers selected from thegroup comprising a soluble medicated film layer; an odor-absorbinglayer; a spreading layer and an additional adhesive layer. The wounddressing may be 2 mm and 4 mm thick. The wound dressing may becharacterized in that the keying layer bonds the absorbent core to aneighboring layer. In some embodiments, the keying layer may bepositioned on either the wound facing side of the absorbent core or thenon-wound facing side of the absorbent core.

In some embodiments, the keying layer is positioned between theabsorbent core and the wound contact layer. The keying layer is apolyamide web.

A more detailed description of the wound dressing of this typehereinabove is provided in EP1718257, the entirety of which is herebyincorporated by reference. In some embodiments, the non-negativepressure wound dressing may be a compression bandage. Compressionbandages are known for use in the treatment of oedema and other venousand lymphatic disorders, e.g., of the lower limbs. A compression bandagesystems typically employ multiple layers including a padding layerbetween the skin and the compression layer or layers. The compressionbandage may be useful for wounds such as handling venous leg ulcers.

The compression bandage in some embodiments may comprise a bandagesystem comprising an inner skin facing layer and an elastic outer layer,the inner layer comprising a first ply of foam and a second ply of anabsorbent nonwoven web, the inner layer and outer layer beingsufficiently elongated so as to be capable of being wound about apatient's limb. A compression bandage of this type is disclosed inWO99/58090, the entirety of which is hereby incorporated by reference.

In some embodiments, the compression bandage system comprises: a) aninner skin facing, elongated, elastic bandage comprising: (i) anelongated, elastic substrate, and (ii) an elongated layer of foam, saidfoam layer being affixed to a face of said substrate and extending 33%or more across said face of substrate in transverse direction and 67% ormore across said face of substrate in longitudinal direction; and b) anouter, elongated, self-adhering elastic bandage; said bandage having acompressive force when extended; wherein, in use, said foam layer of theinner bandage faces the skin and the outer bandage overlies the innerbandage. A compression bandage of this type is disclosed inWO2006/110527, the entirety of which is hereby incorporated byreference. In some embodiments other compression bandage systems such asthose disclosed in U.S. Pat. No. 6,759,566 and US 2002/0099318, theentirety of each of which is hereby incorporated by reference.

Negative Pressure Wound Dressing

In some embodiments, treatment of such wounds can be performed usingnegative pressure wound therapy, wherein a reduced or negative pressurecan be applied to the wound to facilitate and promote healing of thewound. It will also be appreciated that the wound dressing and methodsas disclosed herein may be applied to other parts of the body, and arenot necessarily limited to treatment of wounds.

It will be understood that embodiments of the present disclosure aregenerally applicable to use in topical negative pressure (“TNP”) therapysystems. Briefly, negative pressure wound therapy assists in the closureand healing of many forms of “hard to heal” wounds by reducing tissueoedema; encouraging blood flow and granular tissue formation; removingexcess exudate and may reduce bacterial load (and thus infection risk).In addition, the therapy allows for less disturbance of a wound leadingto more rapid healing. TNP therapy systems may also assist on thehealing of surgically closed wounds by removing fluid and by helping tostabilize the tissue in the apposed position of closure. A furtherbeneficial use of TNP therapy can be found in grafts and flaps whereremoval of excess fluid is important and close proximity of the graft totissue is required in order to ensure tissue viability.

Negative pressure therapy can be used for the treatment of open orchronic wounds that are too large to spontaneously close or otherwisefail to heal by means of applying negative pressure to the site of thewound. Topical negative pressure (TNP) therapy or negative pressurewound therapy (NPWT) involves placing a cover that is impermeable orsemi-permeable to fluids over the wound, using various means to seal thecover to the tissue of the patient surrounding the wound, and connectinga source of negative pressure (such as a vacuum pump) to the cover in amanner so that negative pressure is created and maintained under thecover. It is believed that such negative pressures promote wound healingby facilitating the formation of granulation tissue at the wound siteand assisting the body's normal inflammatory process whilesimultaneously removing excess fluid, which may contain adversecytokines or bacteria.

Some of the dressings used in NPWT can include many different types ofmaterials and layers, for example, gauze, pads, foam pads or multi-layerwound dressings. One example of a multi-layer wound dressing is the PICOdressing, available from Smith & Nephew, includes a wound contact layerand a superabsorbent layer beneath a backing layer to provide acanister-less system for treating a wound with NPWT. The wound dressingmay be sealed to a suction port providing connection to a length oftubing, which may be used to pump fluid out of the dressing or totransmit negative pressure from a pump to the wound dressing.Additionally, RENASYS-F, RENASYS-G, RENASYS-AB, and RENASYS-F/AB,available from Smith & Nephew, are additional examples of NPWT wounddressings and systems. Another example of a multi-layer wound dressingis the ALLEVYN Life dressing, available from Smith & Nephew, whichincludes a moist wound environment dressing that is used to treat thewound without the use of negative pressure.

As is used herein, reduced or negative pressure levels, such as −X mmHg,represent pressure levels relative to normal ambient atmosphericpressure, which can correspond to 760 mmHg (or 1 atm, 29.93 inHg,101.325 kPa, 14.696 psi, etc.). Accordingly, a negative pressure valueof −X mmHg reflects absolute pressure that is X mmHg below 760 mmHg or,in other words, an absolute pressure of (760−X) mmHg. In addition,negative pressure that is “less” or “smaller” than X mmHg corresponds topressure that is closer to atmospheric pressure (such as, −40 mmHg isless than −60 mmHg). Negative pressure that is “more” or “greater” than−X mmHg corresponds to pressure that is further from atmosphericpressure (such as, −80 mmHg is more than −60 mmHg). In some embodiments,local ambient atmospheric pressure is used as a reference point, andsuch local atmospheric pressure may not necessarily be, for example, 760mmHg

The negative pressure range for some embodiments of the presentdisclosure can be approximately −80 mmHg, or between about −20 mmHg and−200 mmHg Note that these pressures are relative to normal ambientatmospheric pressure, which can be 760 mmHg. Thus, −200 mmHg would beabout 560 mmHg in practical terms. In some embodiments, the pressurerange can be between about −40 mmHg and −150 mmHg Alternatively apressure range of up to −75 mmHg, up to −80 mmHg or over −80 mmHg can beused. Also in other embodiments a pressure range of below −75 mmHg canbe used. Alternatively, a pressure range of over approximately −100mmHg, or even −150 mmHg, can be supplied by the negative pressureapparatus.

In some embodiments of wound closure devices described herein, increasedwound contraction can lead to increased tissue expansion in thesurrounding wound tissue. This effect may be increased by varying theforce applied to the tissue, for example by varying the negativepressure applied to the wound over time, possibly in conjunction withincreased tensile forces applied to the wound via embodiments of thewound closure devices. In some embodiments, negative pressure may bevaried over time for example using a sinusoidal wave, square wave, or insynchronization with one or more patient physiological indices (such as,heartbeat). Examples of such applications where additional disclosurerelating to the preceding may be found include U.S. Pat. No. 8,235,955,titled “Wound treatment apparatus and method,” issued on Aug. 7, 2012;and U.S. Pat. No. 7,753,894, titled “Wound cleansing apparatus withstress,” issued Jul. 13, 2010. The disclosures of both of these patentsare hereby incorporated by reference in their entirety.

Embodiments of the wound dressings, wound dressing components, woundtreatment apparatuses and methods described herein may also be used incombination or in addition to those described in InternationalApplication No. PCT/IB2013/001469, filed May 22, 2013, published as WO2013/175306 A2 on Nov. 28, 2013, titled “APPARATUSES AND METHODS FORNEGATIVE PRESSURE WOUND THERAPY,” U.S. patent application Ser. No.14/418,908, filed Jan. 30, 2015, published as US 2015/0190286 A1 on Jul.9, 2015, titled “WOUND DRESSING AND METHOD OF TREATMENT,” thedisclosures of which are hereby incorporated by reference in theirentireties. Embodiments of the wound dressings, wound dressingcomponents, wound treatment apparatuses and methods described herein mayalso be used in combination or in addition to those described in U.S.patent application Ser. No. 13/092,042, filed Apr. 21, 2011, publishedas US2011/0282309, titled “WOUND DRESSING AND METHOD OF USE,” and U.S.patent application Ser. No. 14/715,527, filed May 18, 2015, published asUS2016/0339158 A1 on Nov. 24, 2016, titled “FLUIDIC CONNECTOR FORNEGATIVE PRESSURE WOUND THERAPY,” the disclosure of each of which ishereby incorporated by reference in its entirety, including furtherdetails relating to embodiments of wound dressings, the wound dressingcomponents and principles, and the materials used for the wounddressings.

Additionally, some embodiments related to TNP wound treatment comprisinga wound dressing in combination with a pump or associated electronicsdescribed herein may also be used in combination or in addition to thosedescribed in International Application PCT/EP2016/059329 filed Apr. 26,2016, published as WO 2016/174048 on Nov. 3, 2016, entitled “REDUCEDPRESSURE APPARATUS AND METHODS,” the disclosure of which is herebyincorporated by reference in its entirety.

FIGS. 1A-B illustrate embodiments of a negative pressure wound treatmentsystem 10 employing a wound dressing 100 in conjunction with a fluidicconnector 110. Here, the fluidic connector 110 may comprise an elongateconduit, for example, a bridge 120 having a proximal end 130 and adistal end 140, and an applicator 180 at the distal end 140 of thebridge 120. An optional coupling 160 can be disposed at the proximal end130 of the bridge 120. A cap 170 may be provided with the system (andcan in some cases, as illustrated, be attached to the coupling 160). Thecap 170 can be useful in preventing fluids from leaking out of theproximal end 130. The system 10 may include a source of negativepressure such as a pump or negative pressure unit 150 capable ofsupplying negative pressure. The pump may comprise a canister or othercontainer for the storage of wound exudates and other fluids that may beremoved from the wound. A canister or container may also be providedseparate from the pump. In some embodiments, such as illustrated inFIGS. 1A-1B, the pump 150 can be a canisterless pump such as the PICO™pump, as sold by Smith & Nephew. The pump 150 may be connected to thecoupling 160 via a tube 190, or the pump 150 may be connected directlyto the coupling 160 or directly to the bridge 120. In use, the dressing100 is placed over a suitably-prepared wound, which may in some cases befilled with a wound packing material such as foam or gauze. Theapplicator 180 of the fluidic connector 110 has a sealing surface thatis placed over an aperture in the dressing 100 and is sealed to the topsurface of the dressing 100. Either before, during, or after connectionof the fluidic connector 110 to the dressing 100, the pump 150 isconnected via the tube 190 to the coupling 160, or is connected directlyto the coupling 160 or to the bridge 120. The pump is then activated,thereby supplying negative pressure to the wound. Application ofnegative pressure may be applied until a desired level of healing of thewound is achieved.

As shown in FIG. 2A, the fluidic connector 110 preferably comprises anenlarged distal end, or head 140 that is in fluidic communication withthe dressing 100 as will be described in further detail below. In oneembodiment, the enlarged distal end has a round or circular shape. Thehead 140 is illustrated here as being positioned near an edge of thedressing 100, but may also be positioned at any location on thedressing. For example, some embodiments may provide for a centrally oroff-centered location not on or near an edge or corner of the dressing100. In some embodiments, the dressing 10 may comprise two or morefluidic connectors 110, each comprising one or more heads 140, influidic communication therewith. In a preferred embodiment, the head 140may measure 30 mm along its widest edge. The head 140 forms at least inpart the applicator 180, described above, that is configured to sealagainst a top surface of the wound dressing.

FIG. 2B illustrates a cross-section through a wound dressing 100 similarto the wound dressing 10 as shown in FIG. 1B and described inInternational Patent Publication WO2013175306 A2, which is incorporatedby reference in its entirety, along with fluidic connector 110. Thewound dressing 100, which can alternatively be any wound dressingembodiment disclosed herein or any combination of features of any numberof wound dressing embodiments disclosed herein, can be located in orover a wound to be treated. The dressing 100 may be placed as to form asealed cavity over the wound. In a preferred embodiment, the dressing100 comprises a top or cover layer, or backing layer 220 attached to anoptional wound contact layer 222, both of which are described in greaterdetail below. These two layers 220, 222 are preferably joined or sealedtogether so as to define an interior space or chamber. This interiorspace or chamber may comprise additional structures that may be adaptedto distribute or transmit negative pressure, store wound exudate andother fluids removed from the wound, and other functions which will beexplained in greater detail below. Examples of such structures,described below, include a transmission layer 226 and an absorbent layer221.

As used herein the upper layer, top layer, or layer above refers to alayer furthest from the surface of the skin or wound while the dressingis in use and positioned over the wound. Accordingly, the lower surface,lower layer, bottom layer, or layer below refers to the layer that isclosest to the surface of the skin or wound while the dressing is in useand positioned over the wound.

As illustrated in FIG. 2B, the wound contact layer 222 can be apolyurethane layer or polyethylene layer or other flexible layer whichis perforated, for example via a hot pin process, laser ablationprocess, ultrasound process or in some other way or otherwise madepermeable to liquid and gas. The wound contact layer 222 has a lowersurface 224 and an upper surface 223. The perforations 225 preferablycomprise through holes in the wound contact layer 222 which enable fluidto flow through the layer 222. The wound contact layer 222 helps preventtissue ingrowth into the other material of the wound dressing.Preferably, the perforations are small enough to meet this requirementwhile still allowing fluid to flow therethrough. For example,perforations formed as slits or holes having a size ranging from 0.025mm to 1.2 mm are considered small enough to help prevent tissue ingrowthinto the wound dressing while allowing wound exudate to flow into thedressing. In some configurations, the wound contact layer 222 may helpmaintain the integrity of the entire dressing 100 while also creating anair tight seal around the absorbent pad in order to maintain negativepressure at the wound.

Some embodiments of the wound contact layer 222 may also act as acarrier for an optional lower and upper adhesive layer (not shown). Forexample, a lower pressure sensitive adhesive may be provided on thelower surface 224 of the wound dressing 100 whilst an upper pressuresensitive adhesive layer may be provided on the upper surface 223 of thewound contact layer. The pressure sensitive adhesive, which may be asilicone, hot melt, hydrocolloid or acrylic based adhesive or other suchadhesives, may be formed on both sides or optionally on a selected oneor none of the sides of the wound contact layer. When a lower pressuresensitive adhesive layer is utilized may be helpful to adhere the wounddressing 100 to the skin around a wound. In some embodiments, the woundcontact layer may comprise perforated polyurethane film The lowersurface of the film may be provided with a silicone pressure sensitiveadhesive and the upper surface may be provided with an acrylic pressuresensitive adhesive, which may help the dressing maintain its integrity.In some embodiments, a polyurethane film layer may be provided with anadhesive layer on both its upper surface and lower surface, and allthree layers may be perforated together.

A layer 226 of porous material can be located above the wound contactlayer 222. This porous layer, or transmission layer, 226 allowstransmission of fluid including liquid and gas away from a wound intoupper layers of the wound dressing. In particular, the transmissionlayer 226 preferably ensures that an open air channel can be maintainedto communicate negative pressure over the wound area even when theabsorbent layer has absorbed substantial amounts of exudates. The layer226 should preferably remain open under the typical pressures that willbe applied during negative pressure wound therapy as described above, sothat the whole wound sees an equalized negative pressure. The layer 226may be formed of a material having a three dimensional structure. Forexample, a knitted or woven spacer fabric (for example Baltex 7970 weftknitted polyester) or a non-woven fabric could be used.

In some embodiments, the transmission layer 226 comprises a 3D polyesterspacer fabric layer including a top layer (that is to say, a layerdistal from the wound-bed in use) which is a 84/144 textured polyester,and a bottom layer (that is to say, a layer which lies proximate to thewound bed in use) which is a 10 denier flat polyester and a third layerformed sandwiched between these two layers which is a region defined bya knitted polyester viscose, cellulose or the like mono filament fiber.Other materials and other linear mass densities of fiber could of coursebe used.

Whilst reference is made throughout this disclosure to a monofilamentfiber it will be appreciated that a multistrand alternative could ofcourse be utilized. The top spacer fabric thus has more filaments in ayarn used to form it than the number of filaments making up the yarnused to form the bottom spacer fabric layer.

This differential between filament counts in the spaced apart layershelps control moisture flow across the transmission layer. Particularly,by having a filament count greater in the top layer, that is to say, thetop layer is made from a yarn having more filaments than the yarn usedin the bottom layer, liquid tends to be wicked along the top layer morethan the bottom layer. In use, this differential tends to draw liquidaway from the wound bed and into a central region of the dressing wherethe absorbent layer 221 helps lock the liquid away or itself wicks theliquid onwards towards the cover layer where it can be transpired.

Preferably, to improve the liquid flow across the transmission layer 226(that is to say perpendicular to the channel region formed between thetop and bottom spacer layers, the 3D fabric may be treated with a drycleaning agent (such as, but not limited to, Perchloro Ethylene) to helpremove any manufacturing products such as mineral oils, fats and/orwaxes used previously which might interfere with the hydrophiliccapabilities of the transmission layer. In some embodiments, anadditional manufacturing step can subsequently be carried in which the3D spacer fabric is washed in a hydrophilic agent (such as, but notlimited to, Feran Ice 30 g/l available from the Rudolph Group). Thisprocess step helps ensure that the surface tension on the materials isso low that liquid such as water can enter the fabric as soon as itcontacts the 3D knit fabric. This also aids in controlling the flow ofthe liquid insult component of any exudates.

A layer 221 of absorbent material is provided above the transmissionlayer 226. The absorbent material, which comprise a foam or non-wovennatural or synthetic material, and which may optionally comprise asuper-absorbent material, forms a reservoir for fluid, particularlyliquid, removed from the wound. In some embodiments, the layer 10 mayalso aid in drawing fluids towards the backing layer 220.

The material of the absorbent layer 221 may also prevent liquidcollected in the wound dressing 100 from flowing freely within thedressing, and preferably acts so as to contain any liquid collectedwithin the dressing. The absorbent layer 221 also helps distribute fluidthroughout the layer via a wicking action so that fluid is drawn fromthe wound and stored throughout the absorbent layer. This helps preventagglomeration in areas of the absorbent layer. The capacity of theabsorbent material must be sufficient to manage the exudates flow rateof a wound when negative pressure is applied. Since in use the absorbentlayer experiences negative pressures the material of the absorbent layeris chosen to absorb liquid under such circumstances. A number ofmaterials exist that are able to absorb liquid when under negativepressure, for example superabsorber material. The absorbent layer 221may typically be manufactured from ALLEVYN™ foam, Freudenberg 114-224-4and/or Chem-Posite™11C-450. In some embodiments, the absorbent layer 221may comprise a composite comprising superabsorbent powder, fibrousmaterial such as cellulose, and bonding fibers. In a preferredembodiment, the composite is an airlaid, thermally-bonded composite.

In some embodiments, the absorbent layer 221 is a layer of non-wovencellulose fibers having super-absorbent material in the form of dryparticles dispersed throughout. Use of the cellulose fibers introducesfast wicking elements which help quickly and evenly distribute liquidtaken up by the dressing. The juxtaposition of multiple strand-likefibers leads to strong capillary action in the fibrous pad which helpsdistribute liquid. In this way, the super-absorbent material isefficiently supplied with liquid. The wicking action also assists inbringing liquid into contact with the upper cover layer to aid increasetranspiration rates of the dressing.

An aperture, hole, or orifice 227 is preferably provided in the backinglayer 220 to allow a negative pressure to be applied to the dressing100. The fluidic connector 110 is preferably attached or sealed to thetop of the backing layer 220 over the orifice 227 made into the dressing100, and communicates negative pressure through the orifice 227. Alength of tubing may be coupled at a first end to the fluidic connector110 and at a second end to a pump unit (not shown) to allow fluids to bepumped out of the dressing. Where the fluidic connector is adhered tothe top layer of the wound dressing, a length of tubing may be coupledat a first end of the fluidic connector such that the tubing, orconduit, extends away from the fluidic connector parallel orsubstantially to the top surface of the dressing. The fluidic connector110 may be adhered and sealed to the backing layer 220 using an adhesivesuch as an acrylic, cyanoacrylate, epoxy, UV curable or hot meltadhesive. The fluidic connector 110 may be formed from a soft polymer,for example a polyethylene, a polyvinyl chloride, a silicone orpolyurethane having a hardness of 30 to 90 on the Shore A scale. In someembodiments, the fluidic connector 110 may be made from a soft orconformable material.

Preferably the absorbent layer 221 includes at least one through hole228 located so as to underlie the fluidic connector 110. The throughhole 228 may in some embodiments be the same size as the opening 227 inthe backing layer, or may be bigger or smaller. As illustrated in FIG.2B a single through hole can be used to produce an opening underlyingthe fluidic connector 110. It will be appreciated that multiple openingscould alternatively be utilized. Additionally should more than one portbe utilized according to certain embodiments of the present disclosureone or multiple openings may be made in the absorbent layer and theobscuring layer in registration with each respective fluidic connector.Although not essential to certain embodiments of the present disclosurethe use of through holes in the super-absorbent layer may provide afluid flow pathway which remains unblocked in particular when theabsorbent layer is near saturation.

The aperture or through-hole 228 is preferably provided in the absorbentlayer 221 beneath the orifice 227 such that the orifice is connecteddirectly to the transmission layer 226 as illustrated in FIG. 2B. Thisallows the negative pressure applied to the fluidic connector 110 to becommunicated to the transmission layer 226 without passing through theabsorbent layer 221. This ensures that the negative pressure applied tothe wound is not inhibited by the absorbent layer as it absorbs woundexudates. In other embodiments, no aperture may be provided in theabsorbent layer 221, or alternatively a plurality of aperturesunderlying the orifice 227 may be provided. In further alternativeembodiments, additional layers such as another transmission layer or anobscuring layer such as described in International Patent PublicationWO2014020440, the entirety of which is hereby incorporated by reference,may be provided over the absorbent layer 221 and beneath the backinglayer 220.

The backing layer 220 is preferably gas impermeable, but moisture vaporpermeable, and can extend across the width of the wound dressing 100.The backing layer 220, which may for example be a polyurethane film (forexample, Elastollan SP9109) having a pressure sensitive adhesive on oneside, is impermeable to gas and this layer thus operates to cover thewound and to seal a wound cavity over which the wound dressing isplaced. In this way an effective chamber is made between the backinglayer 220 and a wound where a negative pressure can be established. Thebacking layer 220 is preferably sealed to the wound contact layer 222 ina border region around the circumference of the dressing, ensuring thatno air is drawn in through the border area, for example via adhesive orwelding techniques. The backing layer 220 protects the wound fromexternal bacterial contamination (bacterial barrier) and allows liquidfrom wound exudates to be transferred through the layer and evaporatedfrom the film outer surface. The backing layer 220 preferably comprisestwo layers; a polyurethane film and an adhesive pattern spread onto thefilm. The polyurethane film is preferably moisture vapor permeable andmay be manufactured from a material that has an increased watertransmission rate when wet. In some embodiments the moisture vaporpermeability of the backing layer increases when the backing layerbecomes wet. The moisture vapor permeability of the wet backing layermay be up to about ten times more than the moisture vapor permeabilityof the dry backing layer.

The absorbent layer 221 may be of a greater area than the transmissionlayer 226, such that the absorbent layer overlaps the edges of thetransmission layer 226, thereby ensuring that the transmission layerdoes not contact the backing layer 220. This provides an outer channelof the absorbent layer 221 that is in direct contact with the woundcontact layer 222, which aids more rapid absorption of exudates to theabsorbent layer. Furthermore, this outer channel ensures that no liquidis able to pool around the circumference of the wound cavity, which mayotherwise seep through the seal around the perimeter of the dressingleading to the formation of leaks. As illustrated in FIGS. 2A-2B, theabsorbent layer 221 may define a smaller perimeter than that of thebacking layer 220, such that a boundary or border region is definedbetween the edge of the absorbent layer 221 and the edge of the backinglayer 220.

As shown in FIG. 2B, one embodiment of the wound dressing 100 comprisesan aperture 228 in the absorbent layer 221 situated underneath thefluidic connector 110. In use, for example when negative pressure isapplied to the dressing 100, a wound facing portion of the fluidicconnector may thus come into contact with the transmission layer 226,which can thus aid in transmitting negative pressure to the wound evenwhen the absorbent layer 221 is filled with wound fluids. Someembodiments may have the backing layer 220 be at least partly adhered tothe transmission layer 226. In some embodiments, the aperture 228 is atleast 1-2 mm larger than the diameter of the wound facing portion of thefluidic connector 11, or the orifice 227.

In particular for embodiments with a single fluidic connector 110 andthrough hole, it may be preferable for the fluidic connector 110 andthrough hole to be located in an off-center position as illustrated inFIG. 2A. Such a location may permit the dressing 100 to be positionedonto a patient such that the fluidic connector 110 is raised in relationto the remainder of the dressing 100. So positioned, the fluidicconnector 110 and the filter 214 may be less likely to come into contactwith wound fluids that could prematurely occlude the filter 214 so as toimpair the transmission of negative pressure to the wound.

Turning now to the fluidic connector 110, preferred embodiments comprisea sealing surface 216, a bridge 211 (corresponding to bridge 120 inFIGS. 1A-1B) with a proximal end 130 and a distal end 140, and a filter214. The sealing surface 216 preferably forms the applicator previouslydescribed that is sealed to the top surface of the wound dressing. Insome embodiments a bottom layer of the fluidic connector 110 maycomprise the sealing surface 216. The fluidic connector 110 may furthercomprise an upper surface vertically spaced from the sealing surface216, which in some embodiments is defined by a separate upper layer ofthe fluidic connector. In other embodiments the upper surface and thelower surface may be formed from the same piece of material. In someembodiments the sealing surface 216 may comprise at least one aperture229 therein to communicate with the wound dressing. In some embodimentsthe filter 214 may be positioned across the opening 229 in the sealingsurface, and may span the entire opening 229. The sealing surface 216may be configured for sealing the fluidic connector to the cover layerof the wound dressing, and may comprise an adhesive or weld. In someembodiments, the sealing surface 216 may be placed over an orifice inthe cover layer with optional spacer elements 215 configured to create agap between the filter 214 and the transmission layer 226. In otherembodiments, the sealing surface 216 may be positioned over an orificein the cover layer and an aperture in the absorbent layer 220,permitting the fluidic connector 110 to provide air flow through thetransmission layer 226. In some embodiments, the bridge 211 may comprisea first fluid passage 212 in communication with a source of negativepressure, the first fluid passage 212 comprising a porous material, suchas a 3D knitted material, which may be the same or different than theporous layer 226 described previously. The bridge 211 is preferablyencapsulated by at least one flexible film layer 208, 210 having aproximal and distal end and configured to surround the first fluidpassage 212, the distal end of the flexible film being connected thesealing surface 216. The filter 214 is configured to substantiallyprevent wound exudate from entering the bridge, and spacer elements 215are configured to prevent the fluidic connector from contacting thetransmission layer 226. These elements will be described in greaterdetail below.

Some embodiments may further comprise an optional second fluid passagepositioned above the first fluid passage 212. For example, someembodiments may provide for an air leak may be disposed at the proximalend of the top layer that is configured to provide an air path into thefirst fluid passage 212 and dressing 100 similar to the suction adapteras described in U.S. Pat. No 8,801,685, which is incorporated byreference herein in its entirety.

Preferably, the fluid passage 212 is constructed from a compliantmaterial that is flexible and that also permits fluid to pass through itif the spacer is kinked or folded over. Suitable materials for the fluidpassage 212 include without limitation foams, including open-cell foamssuch as polyethylene or polyurethane foam, meshes, 3D knitted fabrics,non-woven materials, and fluid channels. In some embodiments, the fluidpassage 212 may be constructed from materials similar to those describedabove in relation to the transmission layer 226. Advantageously, suchmaterials used in the fluid passage 212 not only permit greater patientcomfort, but may also provide greater kink resistance, such that thefluid passage 212 is still able to transfer fluid from the wound towardthe source of negative pressure while being kinked or bent.

In some embodiments, the fluid passage 212 may be comprised of a wickingfabric, for example a knitted or woven spacer fabric (such as a knittedpolyester 3D fabric, Baltex 7970®, or Gehring 879®) or a nonwovenfabric. These materials selected are preferably suited to channelingwound exudate away from the wound and for transmitting negative pressureand/or vented air to the wound, and may also confer a degree of kinkingor occlusion resistance to the fluid passage 212. In some embodiments,the wicking fabric may have a three-dimensional structure, which in somecases may aid in wicking fluid or transmitting negative pressure. Incertain embodiments, including wicking fabrics, these materials remainopen and capable of communicating negative pressure to a wound areaunder the typical pressures used in negative pressure therapy, forexample between 40 to 150 mmHg. In some embodiments, the wicking fabricmay comprise several layers of material stacked or layered over eachother, which may in some cases be useful in preventing the fluid passage212 from collapsing under the application of negative pressure. In otherembodiments, the wicking fabric used in the fluid passage 212 may bebetween 1.5 mm and 6 mm; more preferably, the wicking fabric may bebetween 3 mm and 6 mm thick, and may be comprised of either one orseveral individual layers of wicking fabric. In other embodiments, thefluid passage 212 may be between 1.2-3 mm thick, and preferably thickerthan 1.5 mm. Some embodiments, for example a suction adapter used with adressing which retains liquid such as wound exudate, may employhydrophobic layers in the fluid passage 212, and only gases may travelthrough the fluid passage 212. Additionally, and as describedpreviously, the materials used in the system are preferably conformableand soft, which may help to avoid pressure ulcers and othercomplications which may result from a wound treatment system beingpressed against the skin of a patient.

Preferably, the filter element 214 is impermeable to liquids, butpermeable to gases, and is provided to act as a liquid barrier and toensure that no liquids are able to escape from the wound dressing 100.The filter element 214 may also function as a bacterial barrier.Typically the pore size is 0.2 μm. Suitable materials for the filtermaterial of the filter element 214 include 0.2 micron Gore™ expandedPTFE from the MMT range, PALL Versapore™ 200R, and Donaldson™ TX6628.Larger pore sizes can also be used but these may require a secondaryfilter layer to ensure full bioburden containment. As wound fluidcontains lipids it is preferable, though not essential, to use anoleophobic filter membrane for example 1.0 micron MMT-332 prior to 0.2micron MMT-323. This prevents the lipids from blocking the hydrophobicfilter. The filter element can be attached or sealed to the port and/orthe cover film over the orifice. For example, the filter element 214 maybe molded into the fluidic connector 110, or may be adhered to one orboth of the top of the cover layer and bottom of the suction adapter 110using an adhesive such as, but not limited to, a UV cured adhesive.

It will be understood that other types of material could be used for thefilter element 214. More generally a microporous membrane can be usedwhich is a thin, flat sheet of polymeric material, this containsbillions of microscopic pores. Depending upon the membrane chosen thesepores can range in size from 0.01 to more than 10 micrometers.Microporous membranes are available in both hydrophilic (waterfiltering) and hydrophobic (water repellent) forms. In some embodimentsof the invention, filter element 214 comprises a support layer and anacrylic co-polymer membrane formed on the support layer. Preferably thewound dressing 100 according to certain embodiments of the presentinvention uses microporous hydrophobic membranes (MHMs). Numerouspolymers may be employed to form MHMs. For example, the MHMs may beformed from one or more of PTFE, polypropylene, PVDF and acryliccopolymer. All of these optional polymers can be treated in order toobtain specific surface characteristics that can be both hydrophobic andoleophobic. As such these will repel liquids with low surface tensionssuch as multi-vitamin infusions, lipids, surfactants, oils and organicsolvents.

MHMs block liquids whilst allowing air to flow through the membranes.They are also highly efficient air filters eliminating potentiallyinfectious aerosols and particles. A single piece of MHM is well knownas an option to replace mechanical valves or vents. Incorporation ofMHMs can thus reduce product assembly costs improving profits andcosts/benefit ratio to a patient.

The filter element 214 may also include an odor absorbent material, forexample activated charcoal, carbon fiber cloth or Vitec Carbotec-RTQ2003073 foam, or the like. For example, an odor absorbent material mayform a layer of the filter element 214 or may be sandwiched betweenmicroporous hydrophobic membranes within the filter element. The filterelement 214 thus enables gas to be exhausted through the orifice.Liquid, particulates and pathogens however are contained in thedressing.

The wound dressing 100 may comprise spacer elements 215 in conjunctionwith the fluidic connector 110 and the filter 214. With the addition ofsuch spacer elements 215 the fluidic connector 110 and filter 214 may besupported out of direct contact with the absorbent layer 220 and/or thetransmission layer 226. The absorbent layer 220 may also act as anadditional spacer element to keep the filter 214 from contacting thetransmission layer 226. Accordingly, with such a configuration contactof the filter 214 with the transmission layer 226 and wound fluidsduring use may thus be minimized.

Similar to the embodiments of wound dressings described above, somewound dressings comprise a perforated wound contact layer with siliconeadhesive on the skin-contact face and acrylic adhesive on the reverse.Above this bordered layer sits a transmission layer or a 3D spacerfabric pad. Above the transmission layer, sits an absorbent layer. Theabsorbent layer can include a superabsorbent non-woven (NW) pad. Theabsorbent layer can over-border the transmission layer by approximately5 mm at the perimeter. The absorbent layer can have an aperture orthrough-hole toward one end. The aperture can be about 10 mm indiameter. Over the transmission layer and absorbent layer lies a backinglayer. The backing layer can be a high moisture vapor transmission rate(MVTR) film, pattern coated with acrylic adhesive. The high MVTR filmand wound contact layer encapsulate the transmission layer and absorbentlayer, creating a perimeter border of approximately 20 mm. The backinglayer can have a 10 mm aperture that overlies the aperture in theabsorbent layer. Above the hole can be bonded a fluidic connector thatcomprises a liquid-impermeable, gas-permeable semi-permeable membrane(SPM) or filter that overlies the aforementioned apertures.

Turning to FIG. 2C, treatment of other wound types, such as largerabdominal wounds, with negative pressure in certain embodiments uses anegative pressure treatment system 101 as illustrated schematicallyhere. In this embodiment, a wound 106, illustrated here as an abdominalwound, may benefit from treatment with negative pressure. Such abdominalwounds may be a result of, for example, an accident or due to surgicalintervention. In some cases, medical conditions such as abdominalcompartment syndrome, abdominal hypertension, sepsis, or fluid edema mayrequire decompression of the abdomen with a surgical incision throughthe abdominal wall to expose the peritoneal space, after which theopening may need to be maintained in an open, accessible state until thecondition resolves. Other conditions may also necessitate that anopening—particularly in the abdominal cavity—remain open, for example ifmultiple surgical procedures are required (possibly incidental totrauma), or there is evidence of clinical conditions such as peritonitisor necrotizing fasciitis.

In cases where there is a wound, particularly in the abdomen, managementof possible complications relating to the exposure of organs and theperitoneal space is desired, whether or not the wound is to remain openor if it will be closed. Therapy, preferably using the application ofnegative pressure, can be targeted to minimize the risk of infection,while promoting tissue viability and the removal of deleterioussubstances from the wound. The application of reduced or negativepressure to a wound has been found to generally promote faster healing,increased blood flow, decreased bacterial burden, increased rate ofgranulation tissue formation, to stimulate the proliferation offibroblasts, stimulate the proliferation of endothelial cells, closechronic open wounds, inhibit burn penetration, and/or enhance flap andgraft attachment, among other things. It has also been reported thatwounds that have exhibited positive response to treatment by theapplication of negative pressure include infected open wounds, decubitusulcers, dehisced incisions, partial thickness burns, and various lesionsto which flaps or grafts have been attached. Consequently, theapplication of negative pressure to a wound 106 can be beneficial to apatient.

Accordingly, certain embodiments provide for a wound contact layer 105to be placed over the wound 106. The wound contact layer can also bereferred to as an organ protection layer and/or a tissue protectionlayer. Preferably, the wound contact layer 105 can be a thin, flexiblematerial which will not adhere to the wound or the exposed viscera inclose proximity. For example, polymers such as polyurethane,polyethylene, polytetrafluoroethylene, or blends thereof may be used. Inone embodiment, the wound contact layer is permeable. For example, thewound contact layer 105 can be provided with openings, such as holes,slits, or channels, to allow the removal of fluids from the wound 106 orthe transmittal of negative pressure to the wound 106. Additionalembodiments of the wound contact layer 105 are described in furtherdetail below.

Certain embodiments of the negative pressure treatment system 101 mayalso use a porous wound filler 103, which can be disposed over the woundcontact layer 105. This pad 103 can be constructed from a porousmaterial, for example foam, that is soft, resiliently flexible, andgenerally conformable to the wound 106. Such a foam can include anopen-celled and reticulated foam made, for example, of a polymer.Suitable foams include foams composed of, for example, polyurethane,silicone, and polyvinyl alcohol. Preferably, this pad 103 can channelwound exudate and other fluids through itself when negative pressure isapplied to the wound. Some pads 103 may include preformed channels oropenings for such purposes. In certain embodiments, the pad 103 may havea thickness between about one inch and about two inches. The pad mayalso have a length of between about 16 and 17 inches, and a width ofbetween about 11 and 12 inches. In other embodiments, the thickness,width, and/or length can have other suitable values. Other embodimentsof wound fillers that may be used in place of or in addition to the pad103 are discussed in further detail below.

Preferably, a drape 107 is used to seal the wound 106. The drape 107 canbe at least partially liquid impermeable, such that at least a partialnegative pressure may be maintained at the wound. Suitable materials forthe drape 107 include, without limitation, synthetic polymeric materialsthat do not significantly absorb aqueous fluids, including polyolefinssuch as polyethylene and polypropylene, polyurethanes, polysiloxanes,polyamides, polyesters, and other copolymers and mixtures thereof. Thematerials used in the drape may be hydrophobic or hydrophilic. Examplesof suitable materials include Transeal® available from DeRoyal andOpSite® available from Smith & Nephew. In order to aid patient comfortand avoid skin maceration, the drapes in certain embodiments are atleast partly breathable, such that water vapor is able to pass throughwithout remaining trapped under the dressing. An adhesive layer may beprovided on at least a portion the underside of the drape 107 to securethe drape to the skin of the patient, although certain embodiments mayinstead use a separate adhesive or adhesive strip. Optionally, a releaselayer may be disposed over the adhesive layer to protect it prior to useand to facilitate handling the drape 107; in some embodiments, therelease layer may be composed of multiple sections.

The negative pressure system 101 can be connected to a source ofnegative pressure, for example a pump 114. One example of a suitablepump is the Renasys EZ pump available from Smith & Nephew. The drape 107may be connected to the source of negative pressure 114 via a conduit112. The conduit 112 may be connected to a port 113 situated over anaperture 109 in the drape 107, or else the conduit 112 may be connecteddirectly through the aperture 109 without the use of a port. In afurther alternative, the conduit may pass underneath the drape andextend from a side of the drape. U.S. Pat. No. 7,524,315 discloses othersimilar aspects of negative pressure systems and is hereby incorporatedby reference in its entirety and should be considered a part of thisspecification.

In many applications, a container or other storage unit 115 may beinterposed between the source of negative pressure 114 and the conduit112 so as to permit wound exudate and other fluids removed from thewound to be stored without entering the source of negative pressure.Certain types of negative pressure sources—for example, peristalticpumps—may also permit a container 115 to be placed after the pump 114.Some embodiments may also use a filter to prevent fluids, aerosols, andother microbial contaminants from leaving the container 115 and/orentering the source of negative pressure 114. Further embodiments mayalso include a shut-off valve or occluding hydrophobic and/or oleophobicfilter in the container to prevent overflow; other embodiments mayinclude sensing means, such as capacitive sensors or other fluid leveldetectors that act to stop or shut off the source of negative pressureshould the level of fluid in the container be nearing capacity. At thepump exhaust, it may also be preferable to provide an odor filter, suchas an activated charcoal canister.

FIG. 2D illustrates various embodiments of a wound dressing that can beused for healing a wound without negative pressure. As shown in thedressings of FIG. 2D, the wound dressings can have multiple layerssimilar to the dressings described with reference to FIGS. 1A-1B and2A-2B except the dressings of FIG. 2D do not include a port or fluidicconnector. The wound dressings of FIG. 2D can include a cover layer andwound contact layer as described herein. The wound dressing can includevarious layers positioned between the wound contact layer and coverlayer. For example, the dressing can include one or more absorbentlayers and/or one or more transmission layers as described herein withreference to FIGS. 1A-1B and 2A-2B. Additionally, some embodimentsrelated to wound treatment comprising a wound dressing described hereinmay also be used in combination or in addition to those described inU.S. Application Publication No. 2014/0249495, filed May 21, 2014,entitled “WOUND DRESSING AND METHOD OF TREATMENT” the disclosure ofwhich are hereby incorporated by reference in its entirety, includingfurther details relating to embodiments of wound dressings, the wounddressing components and principles, and the materials used for the wounddressings.

A wound dressing that incorporates a number of sensors can be utilizedin order to monitor characteristics of a wound as it heals, providetherapy to the wound, monitor patient movement, etc. Collecting datafrom the wounds that heal well, and from those that do not, can provideuseful insights towards identifying measurands to indicate whether awound is on a healing trajectory.

A number of sensor technologies can be used in wound dressings or one ormore components forming part of an overall wound dressing apparatus. Forexample, as illustrated in FIG. 3A and 3H, sub-sets of sensors can beincorporated onto or into a wound contact layer, which may be aperforated wound contact layer as shown in FIG. 3H. The wound contactlayer in FIG. 3A and 3H is illustrated as having a square shape, but itwill be appreciated that the wound contact layer may have other shapessuch as rectangular, circular, oval, etc. In some embodiments, thesensor integrated wound contact layer can be provided as an individualmaterial layer that is placed over the wound area and then covered by awound dressing apparatus and/or components of a wound dressing apparatussimilar to those described with reference to FIG. 2C (e.g., gauze, foamor other wound packing material, a superabsorbent layer, a drape, afully integrated dressing like the Pico or Allevyn Life dressing, etc.).In other embodiments, the sensor integrated wound contact layer may bepart of a single unit dressing such as described in FIGS. 1A-2B and 2D.

The sensor integrated wound contact layer can be placed in contact withthe wound and will allow fluid to pass through the contact layer whilecausing little to no damage to the tissue in the wound. The sensorintegrated wound contact layer can be made of a flexible material suchas silicone and can incorporate antimicrobials and/or other therapeuticagents known in the art. In some embodiments, the sensor integratedwound contact layer can incorporate adhesives that adhere to wet or drytissue. In some embodiments, the sensors and/or sensor array can beincorporated into or encapsulated within other components of the wounddressing such as the absorbent layer and/or spacer layer describedabove.

As shown in FIGS. 3A and 3H, a sub-set of five sensors can be usedincluding sensors for temperature (e.g., 25 thermistor sensors, in a 5×5array, ˜20 mm pitch), SpO2 (e.g., 4 or 5 SpO2 sensors, in a single linefrom the center of the wound contact layer to the edge thereof, 10 mmpitch), tissue color (e.g., 10 optical sensors, in 2×5 array, ˜20 mmpitch, electrical stimulation (e.g., electrodes), patient movement(e.g., an accelerometer, electromyography (EMG), magnetometer,gyroscope), pH (e.g., by measuring color of a pH-sensitive pad,optionally using the same optical sensors as for tissue color), andconductivity (e.g., 9 conductivity contacts, in a 3×3 array, ˜40 mmpitch). In some instances, more or fewer than five sensor can beutilized. Not all 5 sensors in each row of the array need be aligned. Insome instances, all the sensors can be of the same type. In otherinstances, two or more different types of sensors can be used.

SpO2 is an estimate of arterial oxygen saturation. As shown in FIG. 3A,the SpO2 sensors can be arranged in a single line from the center of ornear the center of the wound contact layer to the edge of the woundcontact layer. The line of SpO2 sensors can allow the sensor to takemeasurements in the middle of the wound, at the edge or the wound,and/or on intact skin to measure changes between the various regions. Insome embodiments, the wound contact layer and/or sensor array can belarger than the size of the wound to cover the entire surface area ofthe wound as well as the surrounding intact skin. The larger size of thewound contact layer and/or sensor array and the multiple sensors canprovide more information about the wound area than if the sensor wasonly placed in the center of the wound or in only one area at a time.

The sensors can be incorporated onto flexible circuit boards formed offlexible polymers including polyamide, polyimide (PI), polyester (PET),polyethylene naphthalate (PEN), polyetherimide (PEI), along with variousfluropolymers (FEP) and copolymers, and/or any material known in theart. The sensor array can be incorporated into a two-layer flexiblecircuit. In some embodiments, the circuit board can be a multi-layerflexible circuit board. In some embodiments, these flexible circuits canbe incorporated into any layer of the wound dressing. In someembodiments, a flexible circuit can be incorporated into a wound contactlayer. For example, the flexible circuit can be incorporated into awound contact layer similar to the wound contact layer described withreference to FIG. 2B and 2C. The wound contact layer can have cutouts orslits that allow for one or more sensors to protrude out of the lowersurface of the wound contact layer and contact the wound area directly.

In some embodiments, the sensor integrated wound contact layer caninclude a first and second wound contact layer with the flexible circuitboard sandwiched between the two layers of wound contact layer material.The first wound contact layer has a lower surface intended to be incontact with the wound and an upper surface intended to be in contactwith flexible circuit board. The second wound contact layer has a lowersurface intended to be in contact with the flexible circuit board and anupper surface intended to be in contact with a wound dressings or one ormore components forming part of an overall wound dressing apparatus. Theupper surface of the first wound contact layer and the lower surface ofthe second wound contact layer can be adhered together with the flexiblecircuit board sandwiched between the two layers.

In some embodiments, the one or more sensors of the flexible circuitboard can be fully encapsulated or covered by the wound contact layersto prevent contact with moisture or fluid in the wound. In someembodiments, the first wound contact layer can have cutouts or slitsthat allow for one or more sensors to protrude out of the lower surfaceand contact the wound area directly. For example, the one or more SpO2sensors as shown in FIG. 3H are shown protruding out the bottom surfaceof the wound contact layer. In some embodiments, the SpO2 sensors can bemounted directly on a lower surface of the first wound contact layer.Some or all of the sensors and electrical components may be potted orencapsulated (rendered waterproof) with a polymer, for example, siliconor epoxy based polymers. The encapsulation with a polymer can preventingress of fluid and leaching of chemicals from the components. In someembodiments, the wound contact layer material can seal the componentsfrom water ingress and leaching of chemicals.

The information gathered from the sensor array and associated wounddressing system can utilize three major components, including a sensorarray, a control module, and software. These components are described inmore detail below.

As described above, the sensor array of FIG. 3A can include athermistor, conductivity sensor, optical sensor, and SpO2 sensor. Theflexible sensor array circuit board 300 includes a sensor array portion301, a tail portion 302, and a connector pad end portion 303 as shown inFIG. 3B. The sensor array portion 301 can include the sensors andassociated circuitry. The sensor array circuit board 300 can include along tail portion 302 extending from the sensor array portion 301. Theconnector pad end portion 303 can be enabled to connect to a controlmodule or other processing unit to receive the data from the sensorarray circuit. The long tail portion 302 can allow the control module tobe placed distant from the wound and in a more convenient location. Anoverall view of one of the sensor arrays circuit board 300 is shown inFIG. 3B.

FIGS. 3C-3F show embodiments of the flexible circuit boards with fourdifferent sensor array geometries. The four different sensor arraygeometries shown are implemented in flexible circuits. While FIGS. 3C-3Fshow four different sensor array formats and configurations, the designas shown in FIG. 3D also shows the connector pads end portion 303.However, the designs of FIGS. 3C, 3E, and 3F can also be created withthe connector pads end portion 303 to allow these flexible circuitboards to communicate with a control module or other processing unit.FIG. 3C-3F illustrate four different sensor array geometries in thesensor array portion 301.

FIG. 3G shows an embodiment of the sensor array portion 301 of thesensor array design shown in FIG. 3D in more detail. In the embodimentsof FIGS. 3A-3G, it will be appreciated that the sensor array portion 301includes a plurality of portions that extend either around a perimeterof a wound dressing component such as a wound contact layer, or inwardfrom an outer edge of the wound dressing component. For example, theembodiments illustrated include a plurality of linearly extendingportions that may be parallel to edges of a wound dressing component,and in some embodiments, follow the entire perimeter of the wounddressing component. In some embodiments, the sensor array portion maycomprise a first plurality of parallel linearly extending portions thatare perpendicular to a second plurality of parallel linearly extendingportions. These linearly extending portions may also have differentlengths and may extend inward to different locations within an interiorof a wound dressing component. The sensor array portion preferably doesnot cover the entire wound dressing component, so that gaps are formedbetween portions of the sensor array. As shown in FIG. 3A, this allowssome, and possibly a majority of the wound dressing component to beuncovered by the sensor array. For example, for a perforated woundcontact layer as shown in FIG. 3A and 3H, the sensor array portion 301may not block a majority of the perforations in the wound contact layer.In some embodiments, the sensor array may also be perforated or shapedto match the perforations in the wound contact layer to minimize theblocking of perforations to fluid flow.

Connectivity for the sensor array can vary depending on the varioussensors and sensor array designs utilized. In some embodiments, as shownin FIG. 3C-3F, a total of 79 connections can be used to connect thecomponents of the sensor array. The sensor arrays can be terminated intwo parallel 40-way 0.5 mm pitch Flat Flexible Cable (FFC) contactsurfaces, with terminals on the top surface, designed to be connected toan FFC connector such as Molex 54104-4031.

In some embodiments, thermistors, conductivity sensors, SpO2 sensors,and/or color sensors can be used on the sensor array to provideinformation relating to conditions of the wound. The sensor array andindividual sensors can assist a clinician in monitoring the healing ofthe wound. The one or more sensors can operate individually or incoordination with each other to provide data relating to the wound andwound healing characteristics.

Temperature sensors can use thermocouples and/or thermistors to measuretemperature. The thermistors can be used to measure and/or track thetemperature of the underlying wound and/or the thermal environmentwithin the wound dressing. The thermometry sensors can be calibrated andthe data obtained from the sensors can be processed to provideinformation about the wound environment. In some embodiments, an ambientsensor measuring ambient air temperature can also be used to assist ineliminating problems associated with environment temperature shifts.

Optical sensors can be used to measure wound appearance using an RGBsensor with an illumination source. In some embodiments, both the RGBsensor and the illumination source would be pressed up against the skin,such that light would penetrate into the tissue and take on the spectralfeatures of the tissue itself.

In some embodiments, pH-changing pads can be used as a pH sensor. Aspectrometer and a broadband white light source can be used to measurethe spectral response of the pH-changing pad. The illumination andimaging can be provided on the surface of the wound dressing that is incontact with the wound and at the bottom surface, which is exposed tofluid. Alternatively, in some embodiments, the illumination and imagingsource can be provided on the surface of the wound dressing opposite thebottom surface and away from fluid application or the top surface of thedressing.

In some embodiments, pulse oximetry SpO2 sensors can be used. To measurehow oxygenated the blood is and the pulsatile blood flow can beobserved. Pulse oximetry measurements work by taking a time resolvedmeasurement of light absorption/transmission in tissue at two differentoptical wavelengths. When hemoglobin becomes oxygenated, its absorptionspectrum changes with regards to non-oxygenated blood. By taking ameasurement at two different wavelengths, one gains a ratio metricmeasure of how oxygenated the blood is.

The components in the sensor array can be connected through multipleconnections. In some embodiments, the thermistors can be arranged ingroups of five. Each thermistor is nominally 10 kΩ, and each group offive has a common ground. There are five groups of thermistors, giving atotal of 30 connections. In some embodiments, there can be nineconductivity terminals. Each conductivity terminal requires oneconnection, giving a total of 9 connections. In some embodiments, therecan be five SpO2 sensors. Each SpO2 sensor requires three connections,plus power and ground (these are covered separately), giving a total of15 connections. In some embodiments, there can be 10 color sensors. Eachcolor sensor comprises an RGB LED and an RGB photodiode. Each colorsensor requires six connections, however five of these are common toevery sensor, giving a total of 15 connections. Power and ground areconsidered separately. In some embodiments, there can be 5 pH sensors.The pH sensors can be a color-change discs, and can be sensed using thecolor sensors described above. Therefore, the pH sensors require noadditional connections. There can be three power rails, and seven groundreturn signals, giving a total of 10 common connections. In someembodiments, the sensor array can include 25 thermistor (MurataNCP15WB473E03RC), 9 conductivity terminal, 5 SpO2 (ADPD144RI), 10 RGBLED (e.g. KPTF-1616RGBC-13), 10 RGB Color Sensor, 10 FET, a PCB, and anassembly.

FIG. 3H illustrates a flexible sensor array incorporated into aperforated wound contact layer according to some embodiments. As shownin FIG. 3H, the PCB sensor array can be sandwiched between two films orwound contact layers. The wound contact layers can have perforationsformed as slits or holes as described herein that are small enough tohelp prevent tissue ingrowth into the wound dressing while allowingwound exudate to flow into the dressing. In some embodiments, the woundcontact layers can have one or more slits that increase flexibility ofthe wound contact layer with integrated sensor array. In someembodiments, one of the wound contact layers can have extra cut outs toaccommodate the sensors so that they can contact the skin directly.

FIG. 31 illustrates a block diagram of a control module according tosome embodiments. The block diagram of the control module includes aconductivity driver box 391 displaying features of the conductivitydriver. Box 392 shows the features of the thermistor interface and box393 shows the features of the optical interface. The control module caninclude a microprocessor with features similar to those shown in box394. Real time clock (RTC), Status LEDs, USB connector, Serial Flash,and Debug Connector can be included as features of the control module asshown in FIG. 31.

In some embodiments, the microprocessor can have one or more of thefollowing requirements: 2.4 GHz radio (either integrated, or external);Supplied Bluetooth software stack; SPI interface; USB (or UART forexternal USB driver); I2C; 3 channel PWM; 32 GPIO; and/or 6-channel ADC.In some embodiments, the device can require at least 48 I/O pins orpossibly more due to banking limitations. Bluetooth stack typicallyrequires ˜20 kB on-board Flash, so a minimum of 32 kB can be required.In some embodiment, 64 kB can be required if complex data processing isconsidered. The processor core can be ARM Cortex M4 or a similarprocessor core. In some embodiments, the parts can include ST'sSTM32L433LC or STM32F302R8, which would require an external radio, orNXP's Kinetis KW range including integrated radio.

In some embodiments, the control module can implement a memory componentwhere the amount of local storage depends on the sample rate andresolution of the sensors. An estimated data requirement of 256 Mb (32MB) is available in a serial Flash device from a number of manufacturers(Micron, Spansion).

The control module can utilize one or more analogue switches. In someembodiments, analogue switches with good on resistance and reasonablebandwidth can be used. For example, Analog Devices' ADG72 or NXP'sNX3L4051HR can be used. Based on the initial system architecture, 8 ofthese will be required.

The control module can incorporate a battery. For example a 300 mWh/daybattery can be used. For 7 days this is 2100 mWh. This could be providedby: a 10 days, non-rechargeable, ER14250 (14.5 mm diameter×25 mm)LiSOCl2 cell; or a 7 days, rechargeable, Li 14500 (14.5 mm diameter×500mm) Li-Ion.

The control module can incorporate a real time clock (RTC). The RTC canbe chosen from any RTC devices with crystal. The control module can alsoinclude miscellaneous resistors, capacitors, connectors, chargecontrollers, and other power supplies.

The PCB of the control module can be a 4-layer board, approximately 50mm×20 mm, or 25 mm×40 mm. The type of PCB used can be largely driven byconnection requirements to sensor array.

The enclosure of the control module can be a two part moulding, withclip features to allow easy access for changing sensor arrays orbatteries.

The data collected through the sensor array can be passed through thecontrol module and processed by a host software. The software may beexecuted on a processing device. The processing device can be a PC,tablet, smartphone, or other computer capable of running host software.The processing device executing the software can be in communicationwith the control module through electrical wires and/or through wirelesscommunication. This software is not to perform the big-data analysis,but to provide access to the data held on the control module. Analysissoftware is beyond the scope of this document. The host software caninclude an interface to the control module via Bluetooth and/or USB. Insome embodiments, the host software can read the status of controlmodule, download logged data from control module, upload sample ratecontrol to control module, convert data from control module into formatsuitable for processing by big-data analysis engine, and/or upload datato cloud for processing by analysis engine.

The software may be developed for PC (Windows/Linux), tablet orsmartphone (Android/iOS), or for multiple platforms.

In some embodiments, a source of negative pressure (such as a pump) andsome or all other components of the topical negative pressure system,such as power source(s), sensor(s), connector(s), user interfacecomponent(s) (such as button(s), switch(es), speaker(s), screen(s),etc.) and the like, can be integral with the wound dressing. In someembodiments, the components can be integrated below, within, on top of,and/or adjacent to the backing layer. In some embodiments, the wounddressing can include a second cover layer and/or a second filter layerfor positioning over the layers of the wound dressing and any of theintegrated components. The second cover layer can be the upper mostlayer of the dressing or can be a separate envelope that enclosed theintegrated components of the topical negative pressure system.

As used herein the upper layer, top layer, or layer above refers to alayer furthest from the surface of the skin or wound while the dressingis in use and positioned over the wound. Accordingly, the lower surface,lower layer, bottom layer, or layer below refers to the layer that isclosest to the surface of the skin or wound while the dressing is in useand positioned over the wound.

Nanosensors

In some embodiments a wound dressing apparatus can incorporate orinclude one or more nanotechnology-enabled sensors (also referred to asnanosensors). The nanosensors can be utilized to measure changes involume, concentration, displacement and velocity, gravitational,electrical, and magnetic forces, pressure, or temperature of cells in abody. Nanosensors may be able to distinguish between or recognizecertain cells at the molecular level in order to deliver medicine ormonitor development to specific places in the body. Nanosensors candetect characteristics of the wound which can be used to, for instance,monitor a wound and recommend a treatment plan based on how well it ishealing. A set of nanosensors can work as a collective community Forexample the nanosensors can communicate as a network and can beformulated into substrates (for example, foams or wound fillers whichcan be placed into a wound cavity).

As described herein with respect to other sensors, nanosensors can beincorporated into an array, a string, a flexible circuit board, amatrix, a chip, etc. In some embodiments, the nanosensors can beelectronically printed on, for instance, a thin, light, disposable orflexible material. In some embodiments, the nanosensors arebiocompatible.

As a wound heals, it can create electric fields. In some embodiments,the nanosensors can interpret and analyze the electrical signals givenoff by a wound. Thus, nanosensors can detect or precisely measure ofthose fields over time, thereby non-invasively tracking a healingprocess of a wound. In some embodiments, the nanosensors can track howfast or how well a wound is healing. In some embodiments, thenanosensors can accelerate wound healing.

In some embodiments, the nanosensors can communicate (for instance usingincorporated antennae) with one or more other sensors or othercommunication device, such as a remote controller. The nanosensor datacan be wirelessly transmitted and analyzed.

Sensor Placement

Accurate placement of a sensor or a sensor array can be important toeffective treatment of a wound or to effective data gathering. Forexample, different locations in and around wound can have drasticallydifferent characteristics. Without knowing where a sensor is located(for example, relative to the wound, other sensors, the patient, etc.),measured data can be misleading or inaccurate, thereby making itdifficult to provide effective treatment to a patient. Accordingly, insome embodiments, one or more techniques are utilized to assist inincreasing the accuracy of the sensor data. For example, one or moretechniques are provided for reducing the chances of imperfect orincorrect placement. In addition, one or more techniques are providedfor increasing the accuracy of sensor data despite imperfect orincorrect placement. Similarly, one or more techniques are providedwhich do not require specific, precise placement of sensors to gatheraccurate information.

In some embodiments, the position or orientation of one or more sensorstrings, sensor strips, sensor arrays, or sensor matrices (generallyreferred to as sensor package), wounds, wound dressings, wound fillers,wound dressing apparatuses, etc. is tracked or determined and may beutilized to limit orientation errors. For example, alignment ororientation considerations may be taken with respect to how a sensorpackage is placed in or onto the wound to ensure that when the sensorpackage is installed or replaced, its orientation in each case is known.This can be necessary to co-reference and cross-reference data. Inaddition, the position or orientation data can be utilized to assist inthe placement (e.g., initial placement or subsequent adjustments) of awound dressing or sensor package to lessen the likelihood of imperfectplacement. In addition, sensor data or sensor functionality can bemodified based on the position or orientation data in order to increasethe accuracy of sensor data despite imperfect placement.

In some embodiments, a sensor package can be utilized to limitorientation errors. For example, it may prove difficult to place asingle sensor in a desired location because, for instance, the sensormay be small or difficult to orient correctly. A sensor package, on theother hand, can be easier to orient because, for example, the increasedsize or potential for orientation markers, as described herein.

In some embodiments, sensors or sensor package can be incorporated intoor encapsulated within a wound dressing or wound packing material. Forexample, the sensors may be stitched into or otherwise permanently orsemi-permanently attached to gauze or durafibre or one or more layers ofthe wound dressing. As another example, the sensors may be mounted ontofoam protrusions which fit into wound. Still, in another example, asensor or sensor package may be deployed into an expandable matrix, foamor other material which fills the wound.

pH Sensing

FIG. 4 illustrates a wound treatment method 400 utilizing pH-sensitivematerial on a wound dressing according to some embodiments. In certainembodiments, a wound dressing or wound packing material comprisingpH-sensitive materials may be placed on or in a wound 402. pH-sensitivematerials may include: pH-sensitive dyes, pH-sensitive pigments,pH-sensitive inks, pH-sensitive superabsorbers, pH-sensitive adhesive ornon-adhesive gels, pH-sensitive adhesive or non-adhesive foams,pH-sensitive hydrophilic polymers, pH-sensitive hydrophobic polymers, orother similar materials. For example, polyurethane gel matrices, such asthose found in the CUTINOVA™ Hydro dressing by Smith & Nephew may besuitable as a pH-sensitive material with some modification. SuchpH-sensitive materials incorporate an element (such as a dye molecule)that will change color at different pH values. As will be understood byone of skill in the art, the pH-sensitive element may be: attacheddirectly to the backbone of the polymer via a chemical bond (such asionic, covalent, and/or polar covalent), adsorbed to the polymer,adhered to the polymer, or attached via some other suitable means. Aswill also be understood by one of skill in the art, pH-sensing orpH-sensitive materials may be used synonymously throughout thisspecification.

In certain embodiments, the pH-sensitive element may be impregnated intospecific types of polyurethanes having a higher hydrophilicity, forexample EU33 (BASF Elastogram SP9109 polyurethane). Alternatively, morehydrophobic polyurethanes may be used, such as Kystsallgran PE399-100.For testing of tensile strength, polyurethanes may be extruded intodumbbell pieces within thicknesses ranging from about 1 mm-10 mm, orabout 2 mm.

Therefore, in some embodiments, a pH-sensitive material will become aparticular color or provide a suitable indicator when exposed to woundexudate in block 404. In certain embodiments, a pH-sensitive element maybe in the form of a triarylmethane dye, a fluorescent dye, or aphenylazo compound. The phenylazo compound may be in the form of2-[4(2-hydroxyethylsulfonyl)-phenyl]diazenyl]-4-methylphenol,1-hydroxy-4-[4[(hydroxyethylsulphonyl)-phenylazo]-napthalene-2-sulphonate,2-fluoro-4-[4[(2-hydroxyethanesulphonyl)-phenylazo]-6-methoxy phenol,4-[4-(2-hydroxyethylsulphonyl)-phenylazo]-2,6-dimethoxyphenol, or othersuitable phenylazo compounds and/or combinations thereof. Furtherdetails regarding such pH-sensitive materials may be found in U.S. Pub.App. No. US2015/0308994A1, filed Nov. 8, 2014 and entitled PH INDICATORDEVICE AND FORMULATION, the entirety of which is incorporated byreference.

As a non-limiting example, a sample preparation protocol was developedfor the preparation of a pH-sensitive material such as disclosed hereinthis specification:

1. Weigh out2-[4(2-hydroxyethylsulfonyl)-phenyl]diazenyl]-4-methylphenol (GJM 514)(32 mg) and4-[4-(2-hydroxyethylsulphonyl)-phenylazo]-2,6-dimethoxyphenol (GJM 534)(18 mg) (1:0.5), add to this 280 μl of sulphuric acid (conc.) and leaveto react for 30 minutes

2. In a 500 ml volumetric flask have 446 ml DI water, add to this thedye solution (after the 30 minutes)

3. To this add 4.0 ml of sodium hydroxide (32% w/v solution, such as 3.2g of sodium hydroxide pellets in 10 ml of deionized water)

4. Then add 50 ml sodium carbonate solution (2.36M), and make up to the500 ml mark with DI water

5. Place polyurethane samples EU33 (BASF Elastogran SP9109 polyurethane)into a beaker

6. Add the dye solution to the polyurethane samples and leave to reactfor 2 hours with stifling

7. Remove the dye solution and then wash with DI water (250 ml) andleave with gentle agitation for a short period of time and then removethe wash solution

8. Repeat this wash step until no more dye appears in the water

9. Wash the sample one last time with DI water (250 ml)

10. The samples will then be evaluated by exposing to an acid solutionthen a basic solution and noting a color change

In some embodiments, the pH-sensing element (also known as a dye) (andthus the pH-sensitive material itself) may become a reddish color whenexposed to acidic conditions (pH 1-6) and become a blueish color whenexposed to basic conditions (pH 8-14). Such a pH-sensing material wouldtherefore change color dependent upon the surrounding medium, forexample wound exudate 402. In certain embodiments, such pH-sensingelements change color along a gradient, such that a highly acidiccondition will be a deeper red, while a highly basic condition may be adeeper blue. Correspondingly, a mildly acidic condition may be a lighterred, such as pink, while a mildly basic condition may be a lighter blue.Colors or red and blue dyes are merely representative, and such dyes mayinvolve a variety of colors or shades, such as dark and light. In someembodiments, pH-sensitive materials may be optimized for a particularrange of pHs, for example a range of about: 1-14, 2-12, 3-11, 4-10. 5-9.6-8. or approximately a pH of 7. In certain embodiments, a pH-sensitivematerial may be tuned for sensing pH in a particular location or medium,for example within a wound. For example, a particular pH-sensing elementmay be optimized to provide high resolution within a narrow band of pHvalues associated with a wound. The pH of a wound may be indicative ofthe healing state of a wound, potentially indicating the presence ofinfection or other wound states.

In certain embodiments, as shown in block 406, a sensor such asdescribed above and/or elsewhere in the specification, for example anoptical sensor, may be positioned such that the optical sensor candetect optical changes in the pH-sensing material. The phrase “opticalsensor” may comprise any optical sensor disclosed herein this section orelsewhere in the specification, with or without a combined light source,the light source comprising any light source described herein thissection or elsewhere in the specification. As described herein, in someembodiments, a pH-sensing material may change color in response tochanges in wound exudate pH, therefore such a color change may bedetectable by the optical sensor in block 406. Such an optical sensormay then be configured to transmit such information to a controller orcomputing system which may convert such optical readings of color changeinto a corresponding pH value as illustrated in block 408 using a pHtable. The controller or computing system may output (visually, audibly,tactilely, or the like) the pH value to a user as shown in block 410 orutilize the pH value in another suitable way. In some embodiments, thecontroller or computing system may provide further information to a userrelating to the consequences of a particular wound pH, such as thepresence of infection and/or impaired healing. In certain embodiments,such an optical sensor may continuously monitor the pH-sensitivematerial, thereby detecting changes in color over time and providingupdated information to the user over time.

A pH-sensing material may comprise any material described herein thissection or elsewhere in the specification, for example, hydrophilicpolymers, foams, and/or gels, both adhesive and non-adhesive. Such foamsmay change color in response to interaction with a liquid (such as woundexudate) and/or a solid surface that has a particular pH. SuchpH-sensitive foam would therefore provide an indication of the pH of theliquid and/or solid surface of interest, depending upon the color of thefoam. In certain embodiments, pH-sensing foam may be created from avariety of techniques. For example, a fully-formed solid foam may besoaked in a liquid comprising a pH-sensitive element (such as a liquiddye), thereby coating the outer surface and potentially the porousinterior of the foam with pH-sensitive elements. In the case of a foamwith unconnected pores and inner channels, only the outer portion of thefoam may be coated. In some embodiments, the pH-sensitive elements maybe added directly to the raw foaming material before and/or duringmixing. Therefore, after solidification into foam, the pH-sensingelements may be distributed throughout the foam. In certain embodiments,the pH-sensing elements may be distributed homogenously orheterogeneously throughout the foam. Distribution of pH-sensing elementsthroughout the foam may be controlled during mixing and formation of thefoam, such that pH-sensing elements are distributed more heavily inareas of the foam that may come into contact with a liquid of interest,such as wound exudate. In certain embodiments, the foam may be chosensuch that the foam has hydrophilic and/or hydrophobic properties.Advantageously, hydrophilic foam may absorb and direct wound exudates,thereby soaking up and sequestering wound exudate for measurement.

Similarly to the foams described herein, in some embodiments, gels,hydrophilic polymers, or other suitable materials described herein thissection or elsewhere in the specification may be impregnated withpH-sensitive elements to thereby allow the gel or other material tochange color upon interaction with a liquid such as wound exudate. Aswith foams, gels or other materials may be soaked in a pH-sensitiveliquid such as a liquid dye, thereby coating the internal and externalsurfaces of the gel with pH-sensitive elements. Similarly, pH-sensitiveelements can incorporated into adhesive gel using a variety oftechniques. For example, the pH-sensitive elements can simply be mixedwith the adhesive gel prior to solidification. As with the foamsdescribed herein, such a gel may be hydrophilic or hydrophobic; however,advantageously, hydrophilic gels may allow for greater sequestering ofwound exudate and therefore better resolution.

As described herein, any optical sensor (such as those described hereinthis section or elsewhere in the specification) and optionally anillumination element may be used in combination with the pH-sensitivematerial to create a pH sensor. For example, a spectrometer and abroadband white light source may be utilized to measure the spectralresponse of the pH-sensitive material. The illumination and imaging canbe provided on the surface of the wound dressing in contact with thewound, for example the bottom surface. However, in some embodiments thesensor or sensors may be positioned on the sides, top, or inside of thedressing. In some embodiments, the illumination and optical sensor maybe provided on the top surface of the wound dressing opposite the bottomsurface containing the pH-sensitive material and measure pH through thedressing. Measurement through the dressing may be particularly enhancedby making the dressing at least partially transparent.

In some embodiments, the optical sensor(s) need not be incorporated intothe wound dressing, instead a color change of the pH-sensitive materialmay be detected utilizing an external device such as a camera on amobile device or smartphone, or other suitable device.

FIG. 5 depicts a wound dressing 500, comprising optical sensors (withoptional light sources) 504 and an adhesive layer 506, the adhesivelayer containing pH-sensitive portions 508 beneath the optical sensorand non-pH sensitive portions 510, the non-pH sensitive portion(s)comprising materials such as any of those described herein this sectionand throughout the specification, except without pH-sensitive elements.For example, the non-pH sensitive portions may comprise hydrophilicadhesive gels or foams that do not contain pH-sensitive elements. Insome embodiments, the pH-sensitive portion may comprise any pH-sensitivematerial described herein this section or elsewhere in thespecification, for example, a pH-sensitive adhesive gel or foam. In someembodiments, such a pH-sensitive material may be transparent, partiallytransparent, or opaque. The wound dressing 500 may comprise but is notlimited to any of the embodiments of wound dressings described above,and may or may not include any of the features of the other wounddressings described herein. The wound dressing 500 of FIG. 5 may also bea component of a wound dressing, and may be a wound filler or a woundpacking material. FIG. 5 illustrates schematically a wound dressinglayer 502 that may be a single layer of a wound dressing, or multiplelayers as described in any of the embodiment above.

Such a pH-sensitive portion may be applied directly to the dressing suchas to the dressing layer 502 via any suitable means, for example byprinting or direct application with an extruder. Advantageously, apH-sensitive adhesive gel or foam may be applied thickly on thedressing, thereby allowing for more sequestration of wound exudate andpotentially greater resolution. A thicker adhesive layer allows for theabsorption of more wound exudate, thereby allowing for a greater rangeof concentration of wound exudate in the range of the optical sensor.Due to the greater concentration of wound exudate in the thickeradhesive material, a greater color delta may be detected by the opticalsensor, thereby providing an improved signal-to-noise ratio. Asdescribed herein, such an approach allows for any optical sensorpositioned in a dressing to become a pH-detecting sensor, simply bycoating the sensor in a layer of pH-sensitive material, such as apH-sensitive gel or foam. The use of a gel or foam advantageously mayimprove resolution compared to a single thin surface layer of printedpH-sensitive dye overlying a portion of the dressing. Further, apH-sensitive material impregnated with pH-sensing elements duringforming will allow for the presence of color changing pH-sensitiveelements throughout the pH-sensitive material, further enhancingresolution.

In certain embodiments and as depicted in the wound monitoring system600 of FIG. 6 (bottom view), wound exudate may be directed via channels602 in a dressing 604 to pH-sensitive material 606 positioned under anoptical sensor 608. In some embodiments, the pH-sensitive material maybe positioned over an optical sensor. Similar to the non-pH sensitiveportions depicted in FIG. 5 above, the channels may comprise anymaterial described herein this section or elsewhere in thespecification, for example hydrophilic foam or gel adhesive. Since suchchannels may be hydrophilic, they may serve to direct wound exudate fromother portions of the dressing to the pH-sensitive material over theoptical sensor, thereby allowing the optical sensor to monitor the pH ofwound exudate even when exudate is only coming into contact with distantportions of the dressing. The channels depicted in FIG. 6 are only onepossible position/orientation of the channels.

In some embodiments, the channels may encompass almost the entirety of aside of the dressing (interspersed with pH-sensitive materials/opticalsensors), be positioned in a staggered pattern, a radial pattern, aspiral pattern, a matrix pattern or any suitable pattern to direct woundexudate to pH-sensitive material overlying one or more optical sensors.

Sensor Normalization

A variety of factors may increase the variability of pH-sensormeasurements over time and within different wounds. For example,variation in lighting, such as via different external light sources,changes in the color characteristics of the pH-sensitive material,changes in the pH-detecting sensor, and other aspects of thesurroundings and the system itself may increase the variability ofsensor measurements. Such variability may decrease the accuracy of colorchange measurements. Therefore, in certain embodiments, opticalpH-detecting sensors such as those described above may need to benormalized/calibrated to a reference material to avoid variability inoptical sensor readings caused by factors other than the actual pHcharacteristics of the wound, such as described above. One of skill inthe art will understand that normalization and calibration may be usedinterchangeably within this disclosure.

FIG. 7 depicts an embodiment of a method for normalizing a pH-detectingsensor, such as the optical sensors described above in relation to FIGS.4-6. In certain embodiments, a reference material with a known andfixed, stable color value may be supplied with the optical sensor andwound dressing described above in relation to FIGS. 4-6. In certainembodiments, the reference material may be supplied separately from thewound dressing, such as in the form of a chip, card, tab or othersuitable format. The reference material may be constructed from anon-absorbent material, such as a non-absorbent solid polymer. In someembodiments, the reference material may be incorporated in the dressing,such as in the top, bottom, or center of the dressing. The referencematerial may be positioned within the dressing such that the opticalsensor may capture the reference material closely in space to thepH-sensitive material, thereby allowing one of skill to directly measureboth the pH-sensitive material and the reference material at the sametime and under the same lighting conditions. By comparing thepH-sensitive material to the reference material, changes in measurementdue to changes in external lighting may be minimized

Such reference material may be of any suitable material, provided thereference material is stable, with a long shelf life, and will notchange in color or other optical characteristics over time. Inembodiments, the reference material may be of any color, such as a colorthe corresponds to the color of the pH-sensitive material across a rangeof pH values corresponding to a wound. For example, the referencematerial may be within the color range of bluish to reddish, such asdescribed above in relation to FIGS. 4-6.

Since the reference material will be of a stable color within differentenvironments, comparison with the reference material will allow forincreased accuracy of the optical sensor. FIG. 7 illustrates a woundtreatment method 700 for utilizing pH-sensitive material and a referencematerial in a wound dressing according to some embodiments. In certainembodiments, a wound dressing or wound filler material comprisingpH-sensitive materials and a reference material may be placed on or in awound 702. Such a dressing may be constructed in any suitable manner,such as described above in relation to FIGS. 4-6. One of skill in theart will understand that the reference material may be incorporated intothe wound dressing or wound filler, but may also be presentedseparately, such as by positioning near the wound dressing or woundfiller such that an optical sensor may still read both the referencematerial and the pH-sensitive material. For a reference material placedwithin a dressing, in embodiments the reference material may bepositioned such that the color of the reference material does not changedue to interaction with wound exudate. Further, as described above, thereference material is preferably non-absorbent, so as to not take up anywound exudate and potential alter the color.

Once the dressing or wound filler is placed in the wound, thepH-sensitive material may become a particular color or provide asuitable indicator when exposed to wound exudate in block 704. Similarto the method described above in relation to FIG. 6, as shown in block706, a sensor such as described above and/or elsewhere in thespecification, for example an optical sensor, may be positioned suchthat the optical sensor can detect optical changes in the pH-sensingmaterial. The phrase “optical sensor” may comprise any optical sensordisclosed herein this section or elsewhere in the specification, with orwithout a combined light source, the light source comprising any lightsource described herein this section or elsewhere in the specification.

As described above in relation to FIGS. 4-6, in some embodiments, apH-sensing material may change color in response to changes in woundexudate pH, therefore such a color change may be detectable by theoptical sensor in block 706. Additionally, the optical sensor may alsocollect color information from the reference material with a fixed knowncolor value. As described elsewhere, the reference material may beincorporated into the dressing or provided separately, provided thereference material is close in space to the pH-sensitive material toaccount for lighting variation and other sources of variability. Theoptical sensor may be constructed or positioned via any suitable meansto collect optical data from both the pH-sensitive material and thereference material. For example, in an optical sensor with multiplesensor clusters, one sensor cluster may read the reference material andanother sensor cluster may read the pH-sensitive material.Alternatively, a system could be set up with single LEDs and singleoptical sensors which then switch between measurements of the referencematerial and pH-sensitive material.

The optical sensor may then transmit such color information for thereference material and the pH-sensitive material to a controller orcomputing system. The controller of computing system may then normalize708 the pH-sensitive material to the reference material, because thereference material has a known, fixed color value. Therefore anydeviation in color value for the reference material from the knownvalue, may also be used to normalize the color value of the pH-sensitivematerial.

Once the color value of the pH-sensitive material is normalized, thecontroller of computing system may convert such optical color readingsinto a corresponding pH value as illustrated in block 710 using a pHtable. The controller or computing system may output (visually, audibly,tactilely, or the like) the pH value to a user as shown in block 712 orutilize the pH value in a another suitable way. In some embodiments, thecontroller or computing system may provide further information to a userrelating to the consequences of a particular wound pH, such as thepresence of infection and/or impaired healing. As described above inrelation to FIGS. 4-6, the measurements for both the pH-sensitivematerial and the reference material may be taken continuously over time,rather than as a snap-shot, such that changes in pH are monitored overtime and automatically normalized.

Other Variations

In some embodiments, one or more electronic components can be positionedon the side of a wound contact layer opposite the side that faces thewound. Systems and methods described herein are equally applicable tosuch wound contact layers. Any wound dressing embodiment describedherein can include features of any of the other described wound dressingembodiments. Similarly, any controller described herein can includefeatures of any of the other described wound dressing embodiments.Further, any device, component, or module described in a certainembodiment can include features of any of the other describedembodiments of the device, component, or module.

Any value of a threshold, limit, duration, etc. provided herein is notintended to be absolute and, thereby, can be approximate. In addition,any threshold, limit, duration, etc. provided herein can be fixed orvaried either automatically or by a user. Furthermore, as is used hereinrelative terminology such as exceeds, greater than, less than, etc. inrelation to a reference value is intended to also encompass being equalto the reference value. For example, exceeding a reference value that ispositive can encompass being equal to or greater than the referencevalue. In addition, as is used herein relative terminology such asexceeds, greater than, less than, etc. in relation to a reference valueis intended to also encompass an inverse of the disclosed relationship,such as below, less than, greater than, etc. in relations to thereference value. Moreover, although blocks of the various processes maybe described in terms of determining whether a value meets or does notmeet a particular threshold, the blocks can be similarly understood, forexample, in terms of a value (i) being below or above a threshold or(ii) satisfying or not satisfying a threshold.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example describedherein unless incompatible therewith. All of the features disclosed inthis specification (including any accompanying claims, abstract anddrawings), or all of the steps of any method or process so disclosed,may be combined in any combination, except combinations where at leastsome of such features or steps are mutually exclusive. The protection isnot restricted to the details of any foregoing embodiments. Theprotection extends to any novel one, or any novel combination, of thefeatures disclosed in this specification (including any accompanyingclaims, abstract and drawings), or to any novel one, or any novelcombination, of the steps of any method or process so disclosed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of protection. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms. Furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made. Those skilled in the art willappreciate that in some embodiments, the actual steps taken in theprocesses illustrated or disclosed may differ from those shown in thefigures. Depending on the embodiment, certain of the steps describedabove may be removed, others may be added. For example, the actual stepsor order of steps taken in the disclosed processes may differ from thoseshown in the figure. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. For instance, thevarious components illustrated in the figures may be implemented assoftware or firmware on a processor, controller, ASIC, FPGA, ordedicated hardware. Hardware components, such as controllers,processors, ASICs, FPGAs, and the like, can include logic circuitry.Furthermore, the features and attributes of the specific embodimentsdisclosed above may be combined in different ways to form additionalembodiments, all of which fall within the scope of the presentdisclosure.

Although the present disclosure includes certain embodiments, examplesand applications, it will be understood by those skilled in the art thatthe present disclosure extends beyond the specifically disclosedembodiments to other alternative embodiments or uses and obviousmodifications and equivalents thereof, including embodiments which donot provide all of the features and advantages set forth herein.Accordingly, the scope of the present disclosure is not intended to belimited by the specific disclosures of preferred embodiments herein, andmay be defined by claims as presented herein or as presented in thefuture.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, or steps are in anyway required for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements, or steps are included orare to be performed in any particular embodiment. The terms“comprising,” “including,” “having,” and the like are synonymous and areused inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Further, the term “each,” as used herein, in addition to having itsordinary meaning, can mean any subset of a set of elements to which theterm “each” is applied.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount. Asanother example, in certain embodiments, the terms “generally parallel”and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees,10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

1. A wound monitoring system, comprising: a wound dressing configured tobe positioned in contact with a wound, the wound dressing comprising anoptical sensor configured to measure a color; and a pH-sensitivematerial positioned on an underside of the wound dressing, thepH-sensitive material configured to change color in response to a changein a pH of the wound, wherein the optical sensor is further configuredto detect the pH of the wound based on detection of the color change ofthe pH-sensitive material.
 2. The system of claim 1, wherein thepH-sensitive material comprises a hydrophilic polymer, a gel, or a foam.3. The system of claim 1, wherein the pH-sensitive material isinterspersed with pH-sensitive elements.
 4. The system of claim 3,wherein the pH-sensitive elements are dispersed heterogeneously.
 5. Thesystem of claim 3, wherein the pH-sensitive elements are dispersedhomogeneously.
 6. The system of claim 1, wherein the pH-sensitivematerial comprises adhesive material.
 7. The system of claim 1, whereinthe pH-sensitive material comprises polyurethane.
 8. The system of claim1, further comprising a non-pH-sensitive material positioned on theunderside of the wound dressing, the non-pH-sensitive materialconfigured to direct wound exudate to the pH-sensitive material.
 9. Thesystem of claim 8, wherein the non-pH-sensitive material comprises ahydrophilic polymer, a gel, or a foam.
 10. The system of claim 8,wherein the non-pH sensitive material is arranged as one or morechannels on the underside of the wound dressing.
 11. The system of claim10, wherein the one or more channels extend from the pH-sensitivematerial to an edge of the dressing.
 12. The system of claim 8, whereinthe non-pH-sensitive material comprises adhesive material.
 13. Thesystem of claim 1, further comprising a controller, the controllerconfigured to convert the color measured by the optical sensor to a pHvalue.
 14. The system of claim 13, wherein the controller is configuredto provide an indication of the pH value to a user.
 15. The system ofclaim 14, wherein the controller is further configured to display the pHvalue.
 16. The system of claim 1, further comprising a referencematerial, the reference material configured to maintain a stable color.17. The system of claim 16, wherein the reference material isincorporated into the wound dressing.
 18. A method of monitoring the pHof a wound, comprising: monitoring at least one of a wound or skinsurrounding a wound with a wound dressing positioned in contact with thewound or skin surrounding the wound, the wound dressing comprising apH-sensitive material configured to change color in response to a changein a pH of the wound and an optical sensor configured to detect a colorchange of the pH-sensitive material; and computing with a processor a pHvalue based on the detected color change from the optical sensor. 19.The method of claim 18, wherein the optical sensor is configured todetect a color value of a reference material, and further comprisingnormalizing a color value of the pH-sensitive material to the referencematerial.
 20. The method of claim 19, wherein the reference material isconfigured to maintain a stable color. 21-24. (Canceled)